Cyclosporine-induced coronary artery constriction - Dissociation between thromboxane release and coronary vasospasm

Cyclosporine influences vascular tone, including that of coronary arteries. But its effect on myocardial prostanoid release, which may contribute to a drug-induced coronary and/or myocardial dysfunction, remains unknown. We u sed the isolated perfused rat heart to study the effect of cyclosporine: on both the mechanical function parameters and myocardial prostanoid release into the effluent by ELISA, Cyclosporine (5 mu M) induced an increase of pe rfusion pressure from 40 +/- 3 to 73 +/- 4 mm Hg within 60 minutes (p < 0.0 01), reflecting an increase of coronary tone. Cyclosporine did not affect h eart rate but contractility (+dp/dt(max)) tended to decrease,although not s ignificantly. The drug's effect on coronary tone was rapidly reversible upo n withdrawal. Cyclosporine perfusion resulted in an increase of thromboxane B-2 liberation from 236 +/- 150 to 1321 +/- 354 pg/ml effluent (p < 0.001) , whereas the 6-ketoprostaglandin F-1 alpha release was unaffected. The veh icle cremophor did not change any of these parameters. Neither inhibition o f myocardial prostanoid formation with acetylsalicylic acid nor thromboxane receptor blockade prevented the cyclosporine-induced increase of perfusion pressure. However, perfusion with nitroglycerin or the voltage-sensitive c alcium channel antagonist nifedipine in addition to cyclosporine were able to prevent the increase of perfusion pressure. This is the first time it ha s been demonstrated that cyclosporine induces an acute release of the prost anoid thromboxane within the myocardium. Despite the resulting imbalance in favor of the vasoconstrictive prostanoid, a dependency of the cyclosporine -induced increase of coronary tone on this imbalance was excluded. Converse ly, nitric oxide donation or calcium channel blockade were able to prevent the negative effect of the drug on coronary tone, supporting the concept of endothelium-dependent and/or myogenic mechanism of cyclosporine toxicity o n the coronary vascular bed.