Br. J. Pharmacol. (1992), 105, 388-392
(D Macmillan Press Ltd, 1992
Increase in vascular permeability produced in rat airways by PAF: potentiation by adrenalectomy 'Piera Boschetto, *Francesco G. Musajo, Laura Tognetto, **Marco Boscaro, ***Cristina E. Mapp, tPeter J. Barnes & Leonardo M. Fabbri Institute of Infectious and Respiratory Diseases, University of Ferrara, Ferrara, Italy; *Department of Surgery, University of Verona, Verona, Italy; **Institute of Semeiotics, University of Padova, Padova, Italy; ***Institute of Occupational Medicine, University of Padova, Padova, Italy and tNational Heart and Lung Institute, London 1 The effect of bilateral adrenalectomy on the sensitivity of blood vessels in rat airways to mediators that increase vascular permeability was examined. 2 An increase in vascular permeability was induced by intravenous platelet activating factor (PAF, 50, 100, 500, 1000 ng kg- 1) and measured by quantifying the extravasation of Evans blue dye. 3 PAF consistently increased the amount of Evans blue extravasation in the larynx, trachea, main bronchi and intrapulmonary airways in sham-operated rats. 4 The magnitude of this extravasation was significantly greater in the larynx (P < 0.05), trachea (P < 0.05) and main bronchi (P < 0.05) of the adrenalectomized rats than it was in these tissues of the sham-operated rats. 5 When adrenalectomized rats were given subcutaneous dexamethasone (0.2mgkg-1 4h before PAF) the amount of plasma extravasation produced by PAF was decreased to the level of the sham-operated rats. 6 We conclude that adrenalectomy potentiates the increase in airway vascular permeability induced by PAF in rats and that this effect may be due to the depletion of endogenous corticosteroids. Keywords: Glucocorticosteroids; airway oedema; anti-inflammatory agents; inflammation; blood vessels; permeability; asthma; PAF. Introduction
Adrenalectomy influences the effect on vascular permeability of different stimuli in different organs or tissues. In rats, adrenalectomy potentiates the vascular permeability induced by histamine and 5-hydroxytryptamine in the skin (Leme & Wilhelm, 1975), the pulmonary vascular permeability induced by hypoxia (Stelzner et al., 1988), and the gastric vascular permeability induced by ethanol (Nishiwaki et al., 1989). Interestingly in all these models, the potentiating effect of adrenalectomy was abolished by exogenous corticosteroids, suggesting that endogenous corticosteroids can diminish the response of blood vessels to certain mediators that increase vascular permeability. In the airways, exogenously administered corticosteroids are potent inhibitors of mediator-induced increase in vascular permeability (Boschetto et al., 1991), whereas it is unknown to what extent endogenously secreted corticosteroids contribute to the natural control of the airway permeability response. In the present study we investigated whether bilateral adrenalectomy enhances the amount of plasma extravasation induced by platelet activating factor (PAF) in rat airways, and whether exogenous corticosteroid replacement prevents the increase of PAF response in adrenalectomized rats. We used rats because it has been demonstrated that corticosteroids are markedly more potent in this species than, for example, in guinea-pigs (Hirshman & Downes, 1985). We have used PAF because it is highly potent in inducing airway vascular permeability (Bussolino et al., 1987; Evans et al., 1987; O'Donnell & Barnett, 1987; Dillon & Duran, 1988). Methods A total of 96 male Sprague-Dawley rats were used, weighing 200-350 g; they were purchased from Morini Farm (Reggio Emilia, Italy). 1 Author for correspondence at: Institute of Infectious and Respiratory Diseases, University of Ferrara, Ferrara, Italy.
Protocol We first examined the increase of airway vascular permeability induced by increasing doses of PAF in adrenalectomized and sham-operated rats, and we observed that adrenalectomy potentiates the response to 500 and 1000 ng kg-1 PAF. Then, we examined the effect of 100ngkg-1 PAF in adrenalectomized and sham-operated rats after pretreatment with subcutaneous dexamethasone. Eighty-four rats were anaesthetized with ether and then bilaterally adrenalectomized or sham-operated (42 rats for each group). These animals were studied between the 7th and 8th day after surgery, based on the observation that adrenalectomy, as previously shown by others (Akana et al., 1985), is associated with depletion of corticosterone at that time. Rats were, then, premedicated with diazepam and anaesthetized with droperidol and fentanyl citrate. In 60 experiments (30 adrenalectomized and 30 sham-operated rats) we first injected Evans blue dye intravenously (i.v.), as a tracer, to assess vascular permeability and 1 min later increasing doses of PAF or of its vehicle. Five minutes after PAF or its vehicle, we opened the chest and perfused the rats through the heart with 0.9% NaCl. Thereafter, we processed larynx, trachea, main bronchi and intrapulmonary airways to determine the amount of plasma extravasation. In the other 36 experiments (12 normal, 12 sham-operated and 12 adrenalectomized rats) animals were treated with dexamethasone or its vehicle 4h before PAF injection.
Bilateral adrenalectomy Eighty-four rats were used throughout the experiments. In each individual experiment, age-matched controls were employed. Bilateral adrenalectomy was carried out under ether anaesthesia. Through small bilateral retroperitoneal incisions, the adrenals were identified at the superior pole of each kidney, removed, and the skin sutured with 3-0 silk. Sham operations were performed in the same manner except that the adrenal glands were left undisturbed. The adrenalectomized rats were given 0.9% NaCI solution for drinking and normal laboratory food. Control animals were given tap water instead of NaCl solution (Caesar et al., 1970). Adrenalectomies
ADRENALECTOMY POTENTIATES AIRWAY VASCULAR PERMEABILITY a
389
a
8060 40
100
-
80
-
60 .
20 40 .
0
20
3
120
O.
I
b
100
160
80
140
60 40 20
120
.fl,
&
100 . 80
0 c
a)
E 0) s 0)
60
220 200 180 160 140 120 100
w
I
a)
I
i
40
:n
20
0)
0
U,
.
[Ll
c
E 220 CD 200 CD
IX
(D Macmillan Press Ltd, 1992
Increase in vascular permeability produced in rat airways by PAF: potentiation by adrenalectomy 'Piera Boschetto, *Francesco G. Musajo, Laura Tognetto, **Marco Boscaro, ***Cristina E. Mapp, tPeter J. Barnes & Leonardo M. Fabbri Institute of Infectious and Respiratory Diseases, University of Ferrara, Ferrara, Italy; *Department of Surgery, University of Verona, Verona, Italy; **Institute of Semeiotics, University of Padova, Padova, Italy; ***Institute of Occupational Medicine, University of Padova, Padova, Italy and tNational Heart and Lung Institute, London 1 The effect of bilateral adrenalectomy on the sensitivity of blood vessels in rat airways to mediators that increase vascular permeability was examined. 2 An increase in vascular permeability was induced by intravenous platelet activating factor (PAF, 50, 100, 500, 1000 ng kg- 1) and measured by quantifying the extravasation of Evans blue dye. 3 PAF consistently increased the amount of Evans blue extravasation in the larynx, trachea, main bronchi and intrapulmonary airways in sham-operated rats. 4 The magnitude of this extravasation was significantly greater in the larynx (P < 0.05), trachea (P < 0.05) and main bronchi (P < 0.05) of the adrenalectomized rats than it was in these tissues of the sham-operated rats. 5 When adrenalectomized rats were given subcutaneous dexamethasone (0.2mgkg-1 4h before PAF) the amount of plasma extravasation produced by PAF was decreased to the level of the sham-operated rats. 6 We conclude that adrenalectomy potentiates the increase in airway vascular permeability induced by PAF in rats and that this effect may be due to the depletion of endogenous corticosteroids. Keywords: Glucocorticosteroids; airway oedema; anti-inflammatory agents; inflammation; blood vessels; permeability; asthma; PAF. Introduction
Adrenalectomy influences the effect on vascular permeability of different stimuli in different organs or tissues. In rats, adrenalectomy potentiates the vascular permeability induced by histamine and 5-hydroxytryptamine in the skin (Leme & Wilhelm, 1975), the pulmonary vascular permeability induced by hypoxia (Stelzner et al., 1988), and the gastric vascular permeability induced by ethanol (Nishiwaki et al., 1989). Interestingly in all these models, the potentiating effect of adrenalectomy was abolished by exogenous corticosteroids, suggesting that endogenous corticosteroids can diminish the response of blood vessels to certain mediators that increase vascular permeability. In the airways, exogenously administered corticosteroids are potent inhibitors of mediator-induced increase in vascular permeability (Boschetto et al., 1991), whereas it is unknown to what extent endogenously secreted corticosteroids contribute to the natural control of the airway permeability response. In the present study we investigated whether bilateral adrenalectomy enhances the amount of plasma extravasation induced by platelet activating factor (PAF) in rat airways, and whether exogenous corticosteroid replacement prevents the increase of PAF response in adrenalectomized rats. We used rats because it has been demonstrated that corticosteroids are markedly more potent in this species than, for example, in guinea-pigs (Hirshman & Downes, 1985). We have used PAF because it is highly potent in inducing airway vascular permeability (Bussolino et al., 1987; Evans et al., 1987; O'Donnell & Barnett, 1987; Dillon & Duran, 1988). Methods A total of 96 male Sprague-Dawley rats were used, weighing 200-350 g; they were purchased from Morini Farm (Reggio Emilia, Italy). 1 Author for correspondence at: Institute of Infectious and Respiratory Diseases, University of Ferrara, Ferrara, Italy.
Protocol We first examined the increase of airway vascular permeability induced by increasing doses of PAF in adrenalectomized and sham-operated rats, and we observed that adrenalectomy potentiates the response to 500 and 1000 ng kg-1 PAF. Then, we examined the effect of 100ngkg-1 PAF in adrenalectomized and sham-operated rats after pretreatment with subcutaneous dexamethasone. Eighty-four rats were anaesthetized with ether and then bilaterally adrenalectomized or sham-operated (42 rats for each group). These animals were studied between the 7th and 8th day after surgery, based on the observation that adrenalectomy, as previously shown by others (Akana et al., 1985), is associated with depletion of corticosterone at that time. Rats were, then, premedicated with diazepam and anaesthetized with droperidol and fentanyl citrate. In 60 experiments (30 adrenalectomized and 30 sham-operated rats) we first injected Evans blue dye intravenously (i.v.), as a tracer, to assess vascular permeability and 1 min later increasing doses of PAF or of its vehicle. Five minutes after PAF or its vehicle, we opened the chest and perfused the rats through the heart with 0.9% NaCl. Thereafter, we processed larynx, trachea, main bronchi and intrapulmonary airways to determine the amount of plasma extravasation. In the other 36 experiments (12 normal, 12 sham-operated and 12 adrenalectomized rats) animals were treated with dexamethasone or its vehicle 4h before PAF injection.
Bilateral adrenalectomy Eighty-four rats were used throughout the experiments. In each individual experiment, age-matched controls were employed. Bilateral adrenalectomy was carried out under ether anaesthesia. Through small bilateral retroperitoneal incisions, the adrenals were identified at the superior pole of each kidney, removed, and the skin sutured with 3-0 silk. Sham operations were performed in the same manner except that the adrenal glands were left undisturbed. The adrenalectomized rats were given 0.9% NaCI solution for drinking and normal laboratory food. Control animals were given tap water instead of NaCl solution (Caesar et al., 1970). Adrenalectomies
ADRENALECTOMY POTENTIATES AIRWAY VASCULAR PERMEABILITY a
389
a
8060 40
100
-
80
-
60 .
20 40 .
0
20
3
120
O.
I
b
100
160
80
140
60 40 20
120
.fl,
&
100 . 80
0 c
a)
E 0) s 0)
60
220 200 180 160 140 120 100
w
I
a)
I
i
40
:n
20
0)
0
U,
.
[Ll
c
E 220 CD 200 CD
IX
