TOSHISHIGE
SHIBAMOTO
AND
JAMES
C. PARKER
Department of Physiology, Division 2, Shinshu University School of Medicine, Matsumoto 390 Department of Physiology, College of Medicine, University of South Alabama, Mobile, Alabama SHIBAMOTO,TOSHISHIGE,AND
JAMES
C.PARKER.F~Z.&~~~
1,6-diphosphate augments paraquat injury in isolated dog lungs. J. Appl. Physiol. 71(5): 1830-1836, 1991.-Paraquat (PQ; l,l’dimethyl-4,4’-bipyridylium dichloride), a widely used herbicide, causes pulmonary edema by a cyclic oxidation and reduction reaction with oxygen molecules with the production of oxygen free radicals. Because fructose 1,6-diphosphate (FDP) has recently been shown to inhibit the generation of oxygen free radicals by activated neutrophils, we determined the effects of FDP on PQ-induced increase in microvascular permeability in isolated blood-perfused dog lungs. Vascular permeability was assessed using the capillary filtration coefficient (I+&,) and isogravimetric capillary pressure (PC,;). There was no change in these variables over 5 h in the control lungs treated with saline (n = 5). A significant increase in K,, and a decrease in Pc,i, both of which indicated increased vascular permeability, were observed at 5 h of perfusion with 4 X low3 M PQ (n = 5). Unexpectedly, an increase in microvascular permeability occurred within 4 h after administration of PQ in the lungs that were pretreated with FDP (2.7-14.2 mM, n = 6). Moreover the increases of I& in the FDP-pretreated lungs were significantly greater than those in the lungs treated with PQ alone. Also, the final-to-initial lung weight ratio of the FDP-pretreated group was greater than those of the other groups. Thus the FDP dose used in the present study accentuated rather than prevented the PQ lung injury. oxygen free radicals; capillary filtration coefficient; isogravimetric capillary pressure; pulmonary edema; vascular permeability
(PQ; l,l’-dimethyl-4,4’-bipyridylium dichloride), a widely used herbicide, causes pulmonary edema and fibrosis in humans and animals (22). When ingested or injected, PQ accumulates preferentially in the lung by an energy-dependent process (17). PQ then appears to exert its toxicity within the cells by a cyclic oxidation by molecular oxygen and reduction at the expense of NADPH, which results in the production of superoxide and other oxygen free radicals and depletion of NADPH. In this way, PQ is generally believed to produce an oxidant lung injury. These toxic oxygen species can produce damage to epithelial and endothelial cells by lipid peroxidation of cell membranes (ZO), by depletion of cellular NADPH stores, or by lysis of alveolar macrophages and neutrophils, causing release of their proteolytic enzymes (24). In fact, a high sensitivity of alveolar macrophages to PQ toxicity has been demonstrated (24). One compound that might preserve cell viability by PARAQUAT
1830
0161-7567/91 $1.50 Copyright
0
preserving intracellular energy stores is fruc phosphate (FDP), an important naturally oc energy intermediate of the glycolytic pathwa been shown to have a beneficial effect in vario shock and in ischemia of various organs (6-12 eficial effect of FDP relates to its regulatory glycolysis, through its action on phosphofru and to its ability to serve as a high-energy under anaerobic conditions (6). On the othe creasing experimental and clinical evidenc that much of the tissue injury in ischemia and shock may result from oxygen free radical within the affected tissues either by tissue or neutrophils. In regard to these mechanisms been shown to inhibit the generation of sup ions (02) and H,O, by activated human and trophils (10, 20). Moreover, pulmonary edema due to a-na urea ((u-NTU), which may be caused in part free radicals (l4), was prevented by FDP (7). appeared likely that FDP might be beneficial ing PQ-induced lung injury. The purpose of study was to determine whether pretreatment would provide protection against PQ-induced lung microvascular permeability in an isol perfused dog lung preparation. METHODS
Isolated lung preparation. Seventeen mo [23.3 t 0.9 (SE) kg] were anesthesized with pe
sodium (30 mg/kg), intubated, and mechanic lated at a tidal volume of 15 ml/kg and at cycles/min. The isolated lung preparation an system have been previously described ( briefly reviewed here. Catheters were placed jugular vein and in the left carotid artery. T anticoagulated with heparin (10,000 U iv) a min was rapidly bled through the carotid arte After left thoracotomy the left lower lobe wa the hilum and weighed. Plastic cannulas wer the pulmonary artery and vein and the loba and perfusion began within 20 min of excisio Lung perfusion system. Figure 1 is a diagram resentation of the perfusion system. The cann was suspended from a strain gauge transduc FT03C; Grass Instrument, Quincy, MA) and constant vascular pressures and at a cons
1991 the American
Physiological
Society
Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (129.081.226.078) on December 11, 2018.
FDP IN PARAQUAT
LUNG
pressure of 3 cmH,O with the shed blood, which was pumped from the venous reservoir through a heat exchanger (37°C) into the arterial reservoir. The height of each reservoir could be independently adjusted to maintain any arterial and venous pressures. The blood was oxygenated at the venous reservoir by bubbling continuously with 95% O,-5% CO,. Pulmonary arterial (Pa) and venous (Pv) pressures were measured with the use of pressure transducers (P23ID; Gould-Statham Instruments, Hato Rey, PR) with zero reference at the level of the lung hilum. Blood flow (Q) was measured with an electromagnetic flowmeter (model 501; Carolina Medical Electronics, King, NC) positioned in the venous outflow line, and lung weight was continuously recorded. Pa and Pv were initially adjusted to maintain perfusion in zone 3 [(Pa > Pv > Paw) where Paw is airway pressure] and to obtain an isogravimetric state (no weight gain or loss). Papaverine (total 4-8 mg) was added to the perfusate to dilate the pulmonary vessels.
1831
INJURY
K f,c
(I)
dPc
Isogravimetric capillary pressure (PC,i). Pc,i is the capil-
lary pressure at which the lung neither weight. The Pc,i is determined by
gains nor loses
Pc,i = Pi + (T(r, - pi)
(2) where 7r, and ri are plasma and interstitial protein oncotic pressures, Pi is interstitial pressure, and 0 is the capillary osmotic reflection coefficient for proteins. Thus a decrease in Pc,i would indicate a decrease in 0 or a decrease in rc, indicating increased vascular permeability to proteins because Pi tends to increase with increased filtration. After obtaining Pc,i, the total vascular (RT),pre- (Ra), and postcapillary (Rv) resistances were calculated as follows
Measurements of Vascular Permeability
RT = (Pa - Pv)/Q
(3)
Ra = (Pa - Pc,i)lQ
(4)
and Rv = (Pc,i - Pv)/Q
(5) was also determined. Experimental protocol. The lung lobe was observed 20 min after the start of perfusion to reach an isogravimetric state at Pa of 13-20 cmH,O, Pv of 3-5 cmH,O, and a blood flow of between 0.7 and 1.40 1. min. 100 g-l. All lobes with a baseline blood flow of
SHIBAMOTO
AND
JAMES
C. PARKER
Department of Physiology, Division 2, Shinshu University School of Medicine, Matsumoto 390 Department of Physiology, College of Medicine, University of South Alabama, Mobile, Alabama SHIBAMOTO,TOSHISHIGE,AND
JAMES
C.PARKER.F~Z.&~~~
1,6-diphosphate augments paraquat injury in isolated dog lungs. J. Appl. Physiol. 71(5): 1830-1836, 1991.-Paraquat (PQ; l,l’dimethyl-4,4’-bipyridylium dichloride), a widely used herbicide, causes pulmonary edema by a cyclic oxidation and reduction reaction with oxygen molecules with the production of oxygen free radicals. Because fructose 1,6-diphosphate (FDP) has recently been shown to inhibit the generation of oxygen free radicals by activated neutrophils, we determined the effects of FDP on PQ-induced increase in microvascular permeability in isolated blood-perfused dog lungs. Vascular permeability was assessed using the capillary filtration coefficient (I+&,) and isogravimetric capillary pressure (PC,;). There was no change in these variables over 5 h in the control lungs treated with saline (n = 5). A significant increase in K,, and a decrease in Pc,i, both of which indicated increased vascular permeability, were observed at 5 h of perfusion with 4 X low3 M PQ (n = 5). Unexpectedly, an increase in microvascular permeability occurred within 4 h after administration of PQ in the lungs that were pretreated with FDP (2.7-14.2 mM, n = 6). Moreover the increases of I& in the FDP-pretreated lungs were significantly greater than those in the lungs treated with PQ alone. Also, the final-to-initial lung weight ratio of the FDP-pretreated group was greater than those of the other groups. Thus the FDP dose used in the present study accentuated rather than prevented the PQ lung injury. oxygen free radicals; capillary filtration coefficient; isogravimetric capillary pressure; pulmonary edema; vascular permeability
(PQ; l,l’-dimethyl-4,4’-bipyridylium dichloride), a widely used herbicide, causes pulmonary edema and fibrosis in humans and animals (22). When ingested or injected, PQ accumulates preferentially in the lung by an energy-dependent process (17). PQ then appears to exert its toxicity within the cells by a cyclic oxidation by molecular oxygen and reduction at the expense of NADPH, which results in the production of superoxide and other oxygen free radicals and depletion of NADPH. In this way, PQ is generally believed to produce an oxidant lung injury. These toxic oxygen species can produce damage to epithelial and endothelial cells by lipid peroxidation of cell membranes (ZO), by depletion of cellular NADPH stores, or by lysis of alveolar macrophages and neutrophils, causing release of their proteolytic enzymes (24). In fact, a high sensitivity of alveolar macrophages to PQ toxicity has been demonstrated (24). One compound that might preserve cell viability by PARAQUAT
1830
0161-7567/91 $1.50 Copyright
0
preserving intracellular energy stores is fruc phosphate (FDP), an important naturally oc energy intermediate of the glycolytic pathwa been shown to have a beneficial effect in vario shock and in ischemia of various organs (6-12 eficial effect of FDP relates to its regulatory glycolysis, through its action on phosphofru and to its ability to serve as a high-energy under anaerobic conditions (6). On the othe creasing experimental and clinical evidenc that much of the tissue injury in ischemia and shock may result from oxygen free radical within the affected tissues either by tissue or neutrophils. In regard to these mechanisms been shown to inhibit the generation of sup ions (02) and H,O, by activated human and trophils (10, 20). Moreover, pulmonary edema due to a-na urea ((u-NTU), which may be caused in part free radicals (l4), was prevented by FDP (7). appeared likely that FDP might be beneficial ing PQ-induced lung injury. The purpose of study was to determine whether pretreatment would provide protection against PQ-induced lung microvascular permeability in an isol perfused dog lung preparation. METHODS
Isolated lung preparation. Seventeen mo [23.3 t 0.9 (SE) kg] were anesthesized with pe
sodium (30 mg/kg), intubated, and mechanic lated at a tidal volume of 15 ml/kg and at cycles/min. The isolated lung preparation an system have been previously described ( briefly reviewed here. Catheters were placed jugular vein and in the left carotid artery. T anticoagulated with heparin (10,000 U iv) a min was rapidly bled through the carotid arte After left thoracotomy the left lower lobe wa the hilum and weighed. Plastic cannulas wer the pulmonary artery and vein and the loba and perfusion began within 20 min of excisio Lung perfusion system. Figure 1 is a diagram resentation of the perfusion system. The cann was suspended from a strain gauge transduc FT03C; Grass Instrument, Quincy, MA) and constant vascular pressures and at a cons
1991 the American
Physiological
Society
Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (129.081.226.078) on December 11, 2018.
FDP IN PARAQUAT
LUNG
pressure of 3 cmH,O with the shed blood, which was pumped from the venous reservoir through a heat exchanger (37°C) into the arterial reservoir. The height of each reservoir could be independently adjusted to maintain any arterial and venous pressures. The blood was oxygenated at the venous reservoir by bubbling continuously with 95% O,-5% CO,. Pulmonary arterial (Pa) and venous (Pv) pressures were measured with the use of pressure transducers (P23ID; Gould-Statham Instruments, Hato Rey, PR) with zero reference at the level of the lung hilum. Blood flow (Q) was measured with an electromagnetic flowmeter (model 501; Carolina Medical Electronics, King, NC) positioned in the venous outflow line, and lung weight was continuously recorded. Pa and Pv were initially adjusted to maintain perfusion in zone 3 [(Pa > Pv > Paw) where Paw is airway pressure] and to obtain an isogravimetric state (no weight gain or loss). Papaverine (total 4-8 mg) was added to the perfusate to dilate the pulmonary vessels.
1831
INJURY
K f,c
(I)
dPc
Isogravimetric capillary pressure (PC,i). Pc,i is the capil-
lary pressure at which the lung neither weight. The Pc,i is determined by
gains nor loses
Pc,i = Pi + (T(r, - pi)
(2) where 7r, and ri are plasma and interstitial protein oncotic pressures, Pi is interstitial pressure, and 0 is the capillary osmotic reflection coefficient for proteins. Thus a decrease in Pc,i would indicate a decrease in 0 or a decrease in rc, indicating increased vascular permeability to proteins because Pi tends to increase with increased filtration. After obtaining Pc,i, the total vascular (RT),pre- (Ra), and postcapillary (Rv) resistances were calculated as follows
Measurements of Vascular Permeability
RT = (Pa - Pv)/Q
(3)
Ra = (Pa - Pc,i)lQ
(4)
and Rv = (Pc,i - Pv)/Q
(5) was also determined. Experimental protocol. The lung lobe was observed 20 min after the start of perfusion to reach an isogravimetric state at Pa of 13-20 cmH,O, Pv of 3-5 cmH,O, and a blood flow of between 0.7 and 1.40 1. min. 100 g-l. All lobes with a baseline blood flow of
