Respiration Physiology (1975) tl, 139-146;
Publishing Company,
North-Holland
Amsterdam
BRADYKINM AND HUMAN AIRWAYS’
HAROLD H. NEWBALL*, HARRY R. KEISER**and The Johns Hopkins
more,
Unioersify
Schoolof
Md. and Hypertension-Endocrine
of
Medicine*, Branch
Health,
l
Deparrmenf
*, National
Bethesda,
of Medicine,
Heart
Mar&and,
and Lung
JOHN J. PISANO** BaltiNational Institutes
5601 Loch Rooer~ Blvd., fnsritute,
U.S.A.
Ahatract. This work explored the effects of bradykinin (BK) on human airways. Bradykinin (1 &kg body weight) was rapidly injected intravenously and respiratory system resistance (Rrs), closing volume (CV), forced vital capacity (FVC), expiratory volume in the first second (FEV,), maximal midexpiratory flow (MMF), and peak flow (PF) were measured. Bradykinin in normals produced no changes in Rrs or CV, but reduced the FVC. This suggests alveolar duct constriction, since no constriction of either large or small airways occurred with the decreased FVC. Bradykinin in asthmatics decreased the Rrs and CV, and increased the FEV,, MMF and PF, while the FVC did not change significantly. The absence of a significant increase in the FVC in the presence of concomitant bronchodilation, suggests that asthmatics also had alveolar duct constriction. These data are consistent with animal studies which show that BK may release adrenalin (or other agents) with secondary elects, such as bronchodilation. The secondary bronchodilation seen in asthmatics but not in normals, is probably a result of the initial higher intrinsic bronchial tone of the asthmatics.
In a guinea pig preparation, James (1969) showed that intraveous bradykinin has a dual effect on the airways, dilating the trachea indirectly through an adrenergic mechanism (abolished by propranolol), and constricting pulmonary airways served by the pulmonary artery. The objective of this report is to suggest that likewise in man, intravenous bradykinin has a dual effect on the airways; dilating the conducting airways (airways proximal to the respiratory bronchioles), while constricting the pulmonary airways served by the pulmonary artery (respiratory bronchioles and the alveolar ducts). for publication 25 February 1975. r The protocol was approved by the NIH Clinical Research Committee, and all patients were fully informed volunteers. Supported in part by a SCOR Grant HL 14153 from the NHLI.
Accepted
139
140
H. H. NEWBALL, H. R. KEISER AND J. J. PISANO
Methods SUBJECTS
The normal subjects were 11 healthy college students, 6 men, 5 women, aged 18 to 21 years, weighing 57-100 kg (74+ 15.2, mean+ SD), who spent 3 months at the National Institutes of Health, as normal volunteers. All volunteers had a negative history of pulmonary disease, and none had a personal or family history of atopic disease. They had normal routine pulmonary function studies klung volumes, flow rates, and diffusing capacity), without significant bronchodilator response to Isuprel. No drugs were taken during the period of our investigation. The asthmatics were 4 men, 6 women, aged 18 to 47 years (32_+ lo), weighing 58 to 93 kg (68.7f 12.3) and hospitalized at the National Institutes of Health during the 3 days of the study. All asthmatics reported a history of extrinsic bronchial asthma. On pulmonary function studies they had reversible airways obstruction (table I), and no evidence of any other lung disease. Patients were not given bronchodilators or other drugs for approximately 24 hours prior to the studies. The severity of the disease was variable, some had symptoms year round, while others had only seasonal symptoms. At the time of the studies, the asthmatics were at their usual asymptomatic state. TABLE 1 Spirometry of ten asthmatic patients. The mean percentage for each parameter significantly increased after Bronkosol
-. FVC FEV, MMF
-
-
Mean + SD -... .-
P .-
85k 17 (99* 14)’ 62+24 (74f 18) 35*27(43+24)
-
~-
-< 0.005 < 0.005 0.01
-..
-_
YValues in parentheses indicate results obtained after inhalation of Bronkosol. Predicted values from Kory t-r al. (1961). Am. J. Med. 30: 243-258. DRUGS
Bradykinin was purchased from Schwarz-Mann, who synthesized it via the solid phase technique of Merrifield (1964). Its purity was confirmed by us with amino acid analysis and chromatography. It was then packaged, lyophilized in siliconized bottles and diluted with normal saline just before use, to a concentration of 25 lg/ml. A placebo injection of 0.9% saline of a volume equal to that of bradykinin was used for each control. EQUIPMENT
Respiratory system resistance was determined by a modification of the forced oscillation technique previously described (Goldman et al., 1970). Respiratory resistance was measured at a constant pressure of 2 cm H,O and a frequency of 3 Hz.
BRADYKININ
AND HUMAN AIRWAYS
141
Closing volume was determined as described by Anthonisen et al. ( 1969/70). Nitrogen was measured by a rapid analyzer (Med-Science, Model 505) and volume change with a Wedge Spirometer (Med-Science, Model 570) the outputs of which were plotted on an X-Y recorder (Hewlett-Packard, Model 7034A). Spirometry was measured with a Stead-Wells spirometer (Warren Collins) which was interfaced to a computer so that all measurements were automated. Functional residual capacity (FRC) was measured with a pressure body plethysmograph box ( DuBois er al.. 1955). PROTOCOL
On day 1 routine pulmonary function, closing volume (CV) measurements and respiratory system resistance (Rrs) were determined in order to familiarize subjects with the equipment. On day 2 an intravenous (iv.) infusion of normal saline was started in a forearm vein and all injections were made via this route. Rrs was measured after rapid injection of a placebo. The same measurement procedure was followed for bradykinin, subjects receiving 1 PgJkg body weight. Respiratory system resistance was measured continuously for 1.5 minute starting at the time of each injection. The average Rrs for all measurable breaths was determined for 30-second intervals. At the end of each Rrs determination, inspiratory capacity was measured. We then measured CV after similar placebo, and bradykinin injections starting approximately 30 seconds after the respective i.v. iniections. Spirometric tests after placebo and bradykinin injections were next determined, with measurements of forced vital capacity (FVC), expiratory volume in the first second (FEV,), maximal midexpiratory flow (MMF) and peak flow (PF). In the normal subjects, a single measurement of the FVC after the placebo injection served as’the control for the four post-bradykinin measurements. It was shown in the same group of normal subjects that the above spirometric parameters did not significantly change when measured at 30-second intervals for 5 minutes. In the asthmatics, 5 FVC measurements at 30-second intervals after the placebo were used to evaluate the respective live postbradykinin observations. The 3 separate injections of bradykinin for measurements of Rrs, CV, and spirometry were about 30 minutes apart. On day 3, measurements of FRC were made at 30-second intervals, after similar placebo and bradykinin injections. After each injection, including the placebo, subjects were asked if they had any side effects. Subjects were unaware of which drug they were receiving on a particular day, or that they would receive a placebo injection. All results were obtained from the net differences of bradykinin minus saline placebo values. The data were analyzed by the t test for paired observation. Results
In all subjects, intravenous bradykinin produced systemic reactions, while placebo produced no reaction in any subject. None of the normal subjects experienced wheezing at any time, while some asthmatics developed transient wheezing. The most frequent symptom was a throbbing headache which was usually gone in 2-5
142
H. H. NEWBALL, H. R. KEISER AND J. J. PISANO
minutes. This was present to variable degrees in 9 of 11 normal subjects and in all 10 asthmatics. Flushing was present in all subjects. Less frequent symptoms included breathlessness, tightness in the chest, palpitations, and local pain at the site of the injection. The symptoms of respiratory distress were transient, persisting for about a minute only, and limited to asthmatics. Several asthmatics mentioned that after the initial transient but often severe respiratory distress, they could breathe easier than before the injection of bradykinin. The inspiratory capacity of all subjects after bradykinin was not significantly different from that after placebo. The FRC measured at 30-second intervals with separate injections of bradykinin did not significantly change over 2.5 minutes. NORMAL SUBJECTS
Average Rrs for 30-second intervals showed no significant difference for bradykinin compared to saline placebo (fig. 1). The mean placebo Rrs of the normals was 4.1 cm H,O/L/sec. The baseline closing volume of the normal subjects ranged from 2.8 to 12.7% (9+ 3.1, mean f SE) and was within normal limits (Buist and Ross, 1973). Bradykinin caused no significant change of the CV (11.85 _+9.6%) from saline placebo, while inducing a small but significant decrease of the FVC (101_+44 ml, P < 0.05) at 90 seconds. There were no significant changes of the FEV,, MMF’or PF.
TIME INTERVAL(seconds) Fig. 1. Effects of intravenous bradykinin on the Rrs of normals and asthmatics. Normal subjects showed a small but progressive decrease of the Rrs, which did not reach levels of significance. Asthmatics showed a significant decrease of the Rrs. ASTHMATIC SUBJECTS
The average Rrs for 30-second intervals significantly decreased with bradykinin compared to the placebo (fig. 1, PC 0.01). The mean placebo Rrs of the asthmatics was 5.5 cm H,O/L/sec. The asthmatics CV ranged from 7.8 to 25.1% ( 17.5 f 6.6) and several were above the normal limits. Bradykinin caused a significant decrease of the CV (- 12%, P=O.O5)with 8 of the 10 asthmatics decreasing their CV. There was no significant change of the FVC; however, there were increases of the FEVr, MMF
143
BRADYKININ AND HUMAN AIRWAYS TABLE 2
Bradykinin induced spirometric changes in asthmatics. Percentage change of bradykinin (B) minus saline (S) placebo at 30-second intervals [(B-.5)/S] x 100. Time (set)
Mean
SE
P
FVC
30 60 90
- 1.63 2.90 4.54
1.61 2.54 3.21
NS NS NS
FEV,
30 60 90
6.06 9.01 5.95
3.90 3.16 4.27
NS < 0.02 NS
MMF
30 60 90
16.96 22.77 6.11
5.62 8.54 3.99
< 0.02 < 0.025 NS
PF
30 60 90
-0.27 8.52 8.67
4.23 3.56 2.37
NS < 0.05 2 mm) contribute about 90% of the airway resistance (Macklem and Mead, 1967). Thus, the measurement of Rrs is a relatively sensitive index of large airway resistance changes (Olive and Hyatt, 1972). Closing volume is reported to be particularly sensitive to changes of the smaller airways (Buist and Ross, 1973), however, one might not expect changes in CV with alveolar duct constriction. The FVC might confirm a gross change, even though it would not pinpoint the site of drug action. NORMAL SUBJECTS
Bradykinin in normal subjects produced no significant change in either the Rrs (fig. 1) or CV; however, there was a significant decrease of the FVC. The decreased FVC in the absence of large airway constriction (no increase of Rrs) or smaller airway constriction (no increase of CV) suggests that the site of action is distal to the small airways, and is probably the alveolar duct. There is some evidence of active closure of alveoli in the human lung during acetylcholine infusion (Emmanuel et al., 1969). There is ample evidence for alveolar duct constriction in animals. Rapid freezing of cat lungs has shown that histamine administered by injection into the right side
144
H. H. NEWBALL.
H. R. KEISER AND J. J. PISANO
of the heart causes alveolar duct constriction (Colebatch, 1968). Data from guinea pig and rabbit suggest that bradykinin has a major effect on the peripheral airways and alveolar ducts (Bhoola et al., 1962). Human alveolar ducts have smooth muscle fibers (Macklin, 1929) so there is the potential for alveolar duct constriction. ASTHMATIC
SUBJECTS
Asthmatics showed significant decreases of the Rrs (fig. 1) and CV, with increases of the FEVr, MMF and PF (table 2). Thus. asthmatics showed bronchodilation of the airways. McCarthy and Milic-Emili (1973) showed that isoproterenol caused a reduction of CV in 18 of 19 asthmatics. Thus, the decreased CV observed in our asthmatics probably represents smaller airways dilation. The absence of a significant increase in the vital capacity in the presence of concomitant airways dilation suggests that bradykinin was having an additional effect distal to the small airways, probably alveolar duct constriction. Bradykinin has been implicated as,a mediator of the acute asthmatic attack (Aas, 1972). The lo-fold elevation above normal of blood kinin reported in severe asthmatics, suggests that kinin release may be involved in the asthmatic attack (Abe er al., 1967). In addition, aerosolized bradykinin significantly decreases peak expiratory flow in asthmatics but not in normals (Varonier and Panzani, 1968). However. Simonsson et al. (1973) have suggested that aerosolized bradykinin induced bronchoconstriction is probably due to nonspecific irritation of vagal irritant receptors. In a guinea pig preparation, James (1969) showed that intravenous bradykinin lowered pressure inside the separated tracheal segment, while it raised pressure inside the pulmonary airways of the lung. A similar dose of bradykinin given into the arch of the aorta lowered pressure in the tracheal segment but did not change the pressure in the pulmonary airways of the lung. The dilating effect of bradykinin on the trachea was abolished by propranolol while the effect of bradykinin on the pulmonary airways was enhanced by propranolol. These studies suggest that bradykinin has a dual effect on the guinea pig airways, dilating the trachea (large airway) via an indirect adrenergic mechanism, while constricting the pulmonary airways served by the pulmonary artery. Our data suggest that likewise in man, intravenous bradykinin has a dual effect on the airways; dilating the conducting airways while constricting the pulmonary airways served by the pulmonary artery - the alveolar ducts. Bradykinin is known to release adrenalin from the cat adrenal medulla (Feldberg and Lewis, 1964) and also to release prostaglandins from the lung (Moncada et al., 1972). Our data suggest that bradykinin releases substances such as adrenalin or prostaglandins E, or E2 which lead to secondary bronchodilation. Fig. 1 shows that after 30 seconds asthmatics demonstrated a significant bronchodilation. These data contirm the statement of most asthmatics, that after the transient initial respiratory distress they could breathe easier than before the injection of bradykinin. The greater sensitivity of asthmatics to bronchodilators is probably a result of an initial higher intrinsic bronchial tone, and may explain the secondary bronchodilation seen in
BRADYKININ
145
AND HUMAN AIRWAYS
asthmatics but not in normals. Intravenous bradykinin in vim ( 1 pg_/kgbody weight) produces no significant constriction of normal human airways (Newball and Keiser, 1973; Newball, 1974). There is probably no primary mediator effect of bradykinin on the larger airways of asthmatics. Bradykinin given intravenously to man probably exerts its primary effects at the level of the alveolar duct. It is unlikely that alveolar duct constriction would increase the work of breathing sufficiently to account for the transient respiratory distress experienced by the asthmatics. However, alveolar duct constriction might lead to distortion or stimulation of pulmonary receptors. sufficient to cause the respiratory distress described. These data suggest that bradykinin is not directly responsible for the large airways constriction observed during the acute asthmatic attack. Bradykinin may, however, have an important mediator effect on the alveolar ducts. Acknowledgement
The author gratefully acknowledges the advice of Dr. Claude Lenfant. References Aas, B. ( 1972). The Biochemical
and Immunological
Basis of Bronchial
Asthma.
Springfield,
C. C. Thomas.
pp. 115-130. Abe. K., N. Watanabe, in patients Anthonisen.
N. Kumagai.
with bronchial
N. R., J. Sanson,
of age. Respir. Physiol. Bhoola.
P. G. Robertson
muscle.
mographic method
method
Eleventh
Springtield.
thoracic capacity
I. Ansari,
Aspen Emphysema
Conference.
Airway
closure as a function
(1962).
Actions
of some peptides
on
volumes
using a modified
single breath
C. C. Thomas,
gas volume: in normal
J. Mead,
of respiratory
(1955).
A rapid
with a nitrogen
plethyswashout
J. C/in. Invest. 35: 322 -326.
and R. Carducci
U.S.P.H.S.,
N. Peterson. resistance
(1969).
Proceedings
from
the
pp. 287-296. by bradykinin
J. R. Schwaber
and angiotension.
P. T. and J. Mead
.I. Physiol.
preparation
M. E. Wohl (1970).
.I. Appl. Physiol. of the guinea
A sim-
28: 113 116.
pig to assess drug
21: 379-386.
( 1967). Resistance ofcentral
J. Appl. Physiol.
and
by forced oscillation.
The use of the in oiuo trachea
on the lung. J. Pharm. Pharmucol.
catheter.
A comparison
subjects.
R. Villano
pp. 169-189.
and J. H. Comroe
171: 98-108.
G. W. L. (1969).
Macklin,
functional
M.. R. J. Knudson,
action
McCarthy,
Dynamics.
Cr. E., A. Rosenbluth,
plifted measurement
Machlem.
values for closing
W. and G. P. Lewis (1964). Release of adrenalin
(London)
James,
and P. G. Shorley
G. N. Bedell, R. Marshall
for measuring
for measuring
Emmanuel,
Goldman,
kinin
19: 19%197.
Predicted
H. J. H. (1968). Airway A. B., S. Y. Botelho,
Feldberg,
plasma
test. Am. Rec. Resp. Dis. 107: 744752.
Colebatch. DuBois.
and W. R. D. Ross (1969/70).
M. Schachter
Brir. J. Pharmacol.
Buist, A. S. and B. B. Ross (1973). nitrogen
(1967). Circulating
23: 626627.
Experienriu
8: 5865.
K. D., H. 0. J. Collier,
bronchial
T. Mouri, T. Seki and K. Yoshinaga
asthma.
and peripheral
airways
measured
by a retrograde
22: 395-401.
C. C. (1929). The musculature D. and J. Milic-Emili
of the bronchi
(1973). Closing
and lungs. Physiol.
volume
in asymptomatic
Rev. 9: 140.
asthma.
Am. Reo. Resp. Dis.
107: 559-570.
Mead. J. (1961). Mechanical Merritield. Moncada,
properties
of lungs. Physiol.
Rec. 41: 281 -330.
R. B. ( 1964). The synthesis of bradykinin. J. Am. Gem. Sot. 86: 304305. S.. S. H. Ferreira and J. R. Vane (1972). Report of the Fifth International
Pharmacology.
New York. Albert J. Phiebig,
Inc., p. 160.
Congress
on
146
H. H. NEWBALL, H. R. KEISER AND J. J. PISANO
Newball, H. H. and H. R. Keiser (1973). Relative effects of bradykinin and histamine on the respiratory system of man. J. Appl. Physiol. 35: 552-556. Newball, H. H. (1974). Response of asthmatic airways to intravenous bradykinin and histamine. Med. Ann. D.C. 43: 111-114. Olive, J. T. and R. E. Hyatt (1972). Maximal expiratory flow and total respiratory resistance during induced bronchoconstriction in asthmatic subjects. Am. Reo. Resp. Dis. 106: 366-376. Simonsson, B. G., B. E. Skoogh, N. P. Beigh, R. Anderson and N. Svedmyr (1973). In oioo and in vitro effect of bradykinin on bronchial motor tone in normal subjects and patients with airways obstruction. Respiration
30: 378-388.
Varonier, H. S. and R. Panzani (1968). The effect of inhalations of bradykinin on healthy and atopic (asthmatic) children. Int. Arch. Allergy 34: 293-296.
Publishing Company,
North-Holland
Amsterdam
BRADYKINM AND HUMAN AIRWAYS’
HAROLD H. NEWBALL*, HARRY R. KEISER**and The Johns Hopkins
more,
Unioersify
Schoolof
Md. and Hypertension-Endocrine
of
Medicine*, Branch
Health,
l
Deparrmenf
*, National
Bethesda,
of Medicine,
Heart
Mar&and,
and Lung
JOHN J. PISANO** BaltiNational Institutes
5601 Loch Rooer~ Blvd., fnsritute,
U.S.A.
Ahatract. This work explored the effects of bradykinin (BK) on human airways. Bradykinin (1 &kg body weight) was rapidly injected intravenously and respiratory system resistance (Rrs), closing volume (CV), forced vital capacity (FVC), expiratory volume in the first second (FEV,), maximal midexpiratory flow (MMF), and peak flow (PF) were measured. Bradykinin in normals produced no changes in Rrs or CV, but reduced the FVC. This suggests alveolar duct constriction, since no constriction of either large or small airways occurred with the decreased FVC. Bradykinin in asthmatics decreased the Rrs and CV, and increased the FEV,, MMF and PF, while the FVC did not change significantly. The absence of a significant increase in the FVC in the presence of concomitant bronchodilation, suggests that asthmatics also had alveolar duct constriction. These data are consistent with animal studies which show that BK may release adrenalin (or other agents) with secondary elects, such as bronchodilation. The secondary bronchodilation seen in asthmatics but not in normals, is probably a result of the initial higher intrinsic bronchial tone of the asthmatics.
In a guinea pig preparation, James (1969) showed that intraveous bradykinin has a dual effect on the airways, dilating the trachea indirectly through an adrenergic mechanism (abolished by propranolol), and constricting pulmonary airways served by the pulmonary artery. The objective of this report is to suggest that likewise in man, intravenous bradykinin has a dual effect on the airways; dilating the conducting airways (airways proximal to the respiratory bronchioles), while constricting the pulmonary airways served by the pulmonary artery (respiratory bronchioles and the alveolar ducts). for publication 25 February 1975. r The protocol was approved by the NIH Clinical Research Committee, and all patients were fully informed volunteers. Supported in part by a SCOR Grant HL 14153 from the NHLI.
Accepted
139
140
H. H. NEWBALL, H. R. KEISER AND J. J. PISANO
Methods SUBJECTS
The normal subjects were 11 healthy college students, 6 men, 5 women, aged 18 to 21 years, weighing 57-100 kg (74+ 15.2, mean+ SD), who spent 3 months at the National Institutes of Health, as normal volunteers. All volunteers had a negative history of pulmonary disease, and none had a personal or family history of atopic disease. They had normal routine pulmonary function studies klung volumes, flow rates, and diffusing capacity), without significant bronchodilator response to Isuprel. No drugs were taken during the period of our investigation. The asthmatics were 4 men, 6 women, aged 18 to 47 years (32_+ lo), weighing 58 to 93 kg (68.7f 12.3) and hospitalized at the National Institutes of Health during the 3 days of the study. All asthmatics reported a history of extrinsic bronchial asthma. On pulmonary function studies they had reversible airways obstruction (table I), and no evidence of any other lung disease. Patients were not given bronchodilators or other drugs for approximately 24 hours prior to the studies. The severity of the disease was variable, some had symptoms year round, while others had only seasonal symptoms. At the time of the studies, the asthmatics were at their usual asymptomatic state. TABLE 1 Spirometry of ten asthmatic patients. The mean percentage for each parameter significantly increased after Bronkosol
-. FVC FEV, MMF
-
-
Mean + SD -... .-
P .-
85k 17 (99* 14)’ 62+24 (74f 18) 35*27(43+24)
-
~-
-< 0.005 < 0.005 0.01
-..
-_
YValues in parentheses indicate results obtained after inhalation of Bronkosol. Predicted values from Kory t-r al. (1961). Am. J. Med. 30: 243-258. DRUGS
Bradykinin was purchased from Schwarz-Mann, who synthesized it via the solid phase technique of Merrifield (1964). Its purity was confirmed by us with amino acid analysis and chromatography. It was then packaged, lyophilized in siliconized bottles and diluted with normal saline just before use, to a concentration of 25 lg/ml. A placebo injection of 0.9% saline of a volume equal to that of bradykinin was used for each control. EQUIPMENT
Respiratory system resistance was determined by a modification of the forced oscillation technique previously described (Goldman et al., 1970). Respiratory resistance was measured at a constant pressure of 2 cm H,O and a frequency of 3 Hz.
BRADYKININ
AND HUMAN AIRWAYS
141
Closing volume was determined as described by Anthonisen et al. ( 1969/70). Nitrogen was measured by a rapid analyzer (Med-Science, Model 505) and volume change with a Wedge Spirometer (Med-Science, Model 570) the outputs of which were plotted on an X-Y recorder (Hewlett-Packard, Model 7034A). Spirometry was measured with a Stead-Wells spirometer (Warren Collins) which was interfaced to a computer so that all measurements were automated. Functional residual capacity (FRC) was measured with a pressure body plethysmograph box ( DuBois er al.. 1955). PROTOCOL
On day 1 routine pulmonary function, closing volume (CV) measurements and respiratory system resistance (Rrs) were determined in order to familiarize subjects with the equipment. On day 2 an intravenous (iv.) infusion of normal saline was started in a forearm vein and all injections were made via this route. Rrs was measured after rapid injection of a placebo. The same measurement procedure was followed for bradykinin, subjects receiving 1 PgJkg body weight. Respiratory system resistance was measured continuously for 1.5 minute starting at the time of each injection. The average Rrs for all measurable breaths was determined for 30-second intervals. At the end of each Rrs determination, inspiratory capacity was measured. We then measured CV after similar placebo, and bradykinin injections starting approximately 30 seconds after the respective i.v. iniections. Spirometric tests after placebo and bradykinin injections were next determined, with measurements of forced vital capacity (FVC), expiratory volume in the first second (FEV,), maximal midexpiratory flow (MMF) and peak flow (PF). In the normal subjects, a single measurement of the FVC after the placebo injection served as’the control for the four post-bradykinin measurements. It was shown in the same group of normal subjects that the above spirometric parameters did not significantly change when measured at 30-second intervals for 5 minutes. In the asthmatics, 5 FVC measurements at 30-second intervals after the placebo were used to evaluate the respective live postbradykinin observations. The 3 separate injections of bradykinin for measurements of Rrs, CV, and spirometry were about 30 minutes apart. On day 3, measurements of FRC were made at 30-second intervals, after similar placebo and bradykinin injections. After each injection, including the placebo, subjects were asked if they had any side effects. Subjects were unaware of which drug they were receiving on a particular day, or that they would receive a placebo injection. All results were obtained from the net differences of bradykinin minus saline placebo values. The data were analyzed by the t test for paired observation. Results
In all subjects, intravenous bradykinin produced systemic reactions, while placebo produced no reaction in any subject. None of the normal subjects experienced wheezing at any time, while some asthmatics developed transient wheezing. The most frequent symptom was a throbbing headache which was usually gone in 2-5
142
H. H. NEWBALL, H. R. KEISER AND J. J. PISANO
minutes. This was present to variable degrees in 9 of 11 normal subjects and in all 10 asthmatics. Flushing was present in all subjects. Less frequent symptoms included breathlessness, tightness in the chest, palpitations, and local pain at the site of the injection. The symptoms of respiratory distress were transient, persisting for about a minute only, and limited to asthmatics. Several asthmatics mentioned that after the initial transient but often severe respiratory distress, they could breathe easier than before the injection of bradykinin. The inspiratory capacity of all subjects after bradykinin was not significantly different from that after placebo. The FRC measured at 30-second intervals with separate injections of bradykinin did not significantly change over 2.5 minutes. NORMAL SUBJECTS
Average Rrs for 30-second intervals showed no significant difference for bradykinin compared to saline placebo (fig. 1). The mean placebo Rrs of the normals was 4.1 cm H,O/L/sec. The baseline closing volume of the normal subjects ranged from 2.8 to 12.7% (9+ 3.1, mean f SE) and was within normal limits (Buist and Ross, 1973). Bradykinin caused no significant change of the CV (11.85 _+9.6%) from saline placebo, while inducing a small but significant decrease of the FVC (101_+44 ml, P < 0.05) at 90 seconds. There were no significant changes of the FEV,, MMF’or PF.
TIME INTERVAL(seconds) Fig. 1. Effects of intravenous bradykinin on the Rrs of normals and asthmatics. Normal subjects showed a small but progressive decrease of the Rrs, which did not reach levels of significance. Asthmatics showed a significant decrease of the Rrs. ASTHMATIC SUBJECTS
The average Rrs for 30-second intervals significantly decreased with bradykinin compared to the placebo (fig. 1, PC 0.01). The mean placebo Rrs of the asthmatics was 5.5 cm H,O/L/sec. The asthmatics CV ranged from 7.8 to 25.1% ( 17.5 f 6.6) and several were above the normal limits. Bradykinin caused a significant decrease of the CV (- 12%, P=O.O5)with 8 of the 10 asthmatics decreasing their CV. There was no significant change of the FVC; however, there were increases of the FEVr, MMF
143
BRADYKININ AND HUMAN AIRWAYS TABLE 2
Bradykinin induced spirometric changes in asthmatics. Percentage change of bradykinin (B) minus saline (S) placebo at 30-second intervals [(B-.5)/S] x 100. Time (set)
Mean
SE
P
FVC
30 60 90
- 1.63 2.90 4.54
1.61 2.54 3.21
NS NS NS
FEV,
30 60 90
6.06 9.01 5.95
3.90 3.16 4.27
NS < 0.02 NS
MMF
30 60 90
16.96 22.77 6.11
5.62 8.54 3.99
< 0.02 < 0.025 NS
PF
30 60 90
-0.27 8.52 8.67
4.23 3.56 2.37
NS < 0.05 2 mm) contribute about 90% of the airway resistance (Macklem and Mead, 1967). Thus, the measurement of Rrs is a relatively sensitive index of large airway resistance changes (Olive and Hyatt, 1972). Closing volume is reported to be particularly sensitive to changes of the smaller airways (Buist and Ross, 1973), however, one might not expect changes in CV with alveolar duct constriction. The FVC might confirm a gross change, even though it would not pinpoint the site of drug action. NORMAL SUBJECTS
Bradykinin in normal subjects produced no significant change in either the Rrs (fig. 1) or CV; however, there was a significant decrease of the FVC. The decreased FVC in the absence of large airway constriction (no increase of Rrs) or smaller airway constriction (no increase of CV) suggests that the site of action is distal to the small airways, and is probably the alveolar duct. There is some evidence of active closure of alveoli in the human lung during acetylcholine infusion (Emmanuel et al., 1969). There is ample evidence for alveolar duct constriction in animals. Rapid freezing of cat lungs has shown that histamine administered by injection into the right side
144
H. H. NEWBALL.
H. R. KEISER AND J. J. PISANO
of the heart causes alveolar duct constriction (Colebatch, 1968). Data from guinea pig and rabbit suggest that bradykinin has a major effect on the peripheral airways and alveolar ducts (Bhoola et al., 1962). Human alveolar ducts have smooth muscle fibers (Macklin, 1929) so there is the potential for alveolar duct constriction. ASTHMATIC
SUBJECTS
Asthmatics showed significant decreases of the Rrs (fig. 1) and CV, with increases of the FEVr, MMF and PF (table 2). Thus. asthmatics showed bronchodilation of the airways. McCarthy and Milic-Emili (1973) showed that isoproterenol caused a reduction of CV in 18 of 19 asthmatics. Thus, the decreased CV observed in our asthmatics probably represents smaller airways dilation. The absence of a significant increase in the vital capacity in the presence of concomitant airways dilation suggests that bradykinin was having an additional effect distal to the small airways, probably alveolar duct constriction. Bradykinin has been implicated as,a mediator of the acute asthmatic attack (Aas, 1972). The lo-fold elevation above normal of blood kinin reported in severe asthmatics, suggests that kinin release may be involved in the asthmatic attack (Abe er al., 1967). In addition, aerosolized bradykinin significantly decreases peak expiratory flow in asthmatics but not in normals (Varonier and Panzani, 1968). However. Simonsson et al. (1973) have suggested that aerosolized bradykinin induced bronchoconstriction is probably due to nonspecific irritation of vagal irritant receptors. In a guinea pig preparation, James (1969) showed that intravenous bradykinin lowered pressure inside the separated tracheal segment, while it raised pressure inside the pulmonary airways of the lung. A similar dose of bradykinin given into the arch of the aorta lowered pressure in the tracheal segment but did not change the pressure in the pulmonary airways of the lung. The dilating effect of bradykinin on the trachea was abolished by propranolol while the effect of bradykinin on the pulmonary airways was enhanced by propranolol. These studies suggest that bradykinin has a dual effect on the guinea pig airways, dilating the trachea (large airway) via an indirect adrenergic mechanism, while constricting the pulmonary airways served by the pulmonary artery. Our data suggest that likewise in man, intravenous bradykinin has a dual effect on the airways; dilating the conducting airways while constricting the pulmonary airways served by the pulmonary artery - the alveolar ducts. Bradykinin is known to release adrenalin from the cat adrenal medulla (Feldberg and Lewis, 1964) and also to release prostaglandins from the lung (Moncada et al., 1972). Our data suggest that bradykinin releases substances such as adrenalin or prostaglandins E, or E2 which lead to secondary bronchodilation. Fig. 1 shows that after 30 seconds asthmatics demonstrated a significant bronchodilation. These data contirm the statement of most asthmatics, that after the transient initial respiratory distress they could breathe easier than before the injection of bradykinin. The greater sensitivity of asthmatics to bronchodilators is probably a result of an initial higher intrinsic bronchial tone, and may explain the secondary bronchodilation seen in
BRADYKININ
145
AND HUMAN AIRWAYS
asthmatics but not in normals. Intravenous bradykinin in vim ( 1 pg_/kgbody weight) produces no significant constriction of normal human airways (Newball and Keiser, 1973; Newball, 1974). There is probably no primary mediator effect of bradykinin on the larger airways of asthmatics. Bradykinin given intravenously to man probably exerts its primary effects at the level of the alveolar duct. It is unlikely that alveolar duct constriction would increase the work of breathing sufficiently to account for the transient respiratory distress experienced by the asthmatics. However, alveolar duct constriction might lead to distortion or stimulation of pulmonary receptors. sufficient to cause the respiratory distress described. These data suggest that bradykinin is not directly responsible for the large airways constriction observed during the acute asthmatic attack. Bradykinin may, however, have an important mediator effect on the alveolar ducts. Acknowledgement
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