L-arginine prevents cyclosporin A-induced pulmonary vascular dysfunction.
BACKGROUND
Cyclosporin A is known to alter endothelium-dependent responses to different agonists. Few data are available concerning the effect of cyclosporin A on the pulmonary vascular bed.


METHODS
The endothelium-dependent responses to acetylcholine (20 micrograms), bradykinin (5 micrograms), and substance P (5 micrograms) were investigated in a dog model of left lung autoperfusion at constant flow.


RESULTS
The vasodilator response to bradykinin and substance P was significantly decreased with cyclosporin A (20 mg) administration. The average decreases in pulmonary arterial pressure with bradykinin were 5.4 +/- 1.5 mm Hg and 2.4 +/- 0.4 mm Hg before and after cyclosporin A administration, respectively (p = 0.04). The average decreases in pulmonary arterial pressure with substance P were 4.4 +/- 1.0 mm Hg and 1.8 +/- 0.5 mm Hg before and after cyclosporin A administration, respectively (p = 0.04). The responses to acetylcholine and the endothelium-independent relaxing agent nitroglycerin were not significantly affected by cyclosporin A. The effects of cyclosporin A on endothelium-dependent responses to bradykinin and substance P were overcome by the administration of L-arginine (200 mg/kg intravenously). The decreased response to bradykinin and substance P after cyclosporin A administration was not significantly affected by indomethacin, a cyclooxygenase inhibitor. The pulmonary angiotensin-converting enzyme activity was also measured using [3H]benzoyl-phenylalanyl-glycyl-proline, an inactive angiotensin-converting enzyme substrate. There was an average [3H]benzoyl-phenylalanyl-glycyl-proline hydrolysis of 54% +/- 2% and 55% +/- 2% before and after cyclosporin A administration, respectively (not significant).


CONCLUSIONS
The present study suggests that cyclosporin A selectively decreases endothelium-dependent responses to bradykinin and substance P without affecting the cyclic guanosine monophosphate-dependent pathway in the canine pulmonary vascular bed. The decreased endothelium-dependent responses to bradykinin and substance P are not related to increased angiotensin-converting enzyme activity. The toxic effect of cyclosporin A on endothelium-dependent responses is reversible by the administration of L-arginine, a source of substrate for nitric oxide.
Mathieu
P
P
Department of Medicine, Montreal Heart Institute, Quebec, Canada.
Carrier
M
M
Dupuis
J
J
Ryan
J
J
Pelletier
L C
LC
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D016279:Atrial Function, Left / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D016572:Cyclosporine / Q000633:toxicity*; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D007213:Indomethacin / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D005996:Nitroglycerin / Q000494:pharmacology; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism; D011651:Pulmonary Artery; D011652:Pulmonary Circulation / Q000187:drug effects* / Q000502:physiology; D013373:Substance P / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D016861:Cyclooxygenase Inhibitors; D014665:Vasodilator Agents; D013373:Substance P; D016572:Cyclosporine; D001120:Arginine; D019001:Nitric Oxide Synthase; D007703:Peptidyl-Dipeptidase A; D005996:Nitroglycerin; D000109:Acetylcholine; D001920:Bradykinin; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin