[Cyclosporine A decreases coronary blood flow in dogs]

The objective of the present study was to determine the effect of cyclosporine (CSA) on coronary artery reactivity. Six mongrel dogs, weighing 20 to 30 kg were anesthetized with sodium pentobarbital and were artificially ventilated. A median sternotomy was performed to expose the heart. Left anterior and circumflex coronary flows were measured with an electromagnetic flowmeter. Heart rate, mean arterial pressure, coronary sinus pressure and dP/dt were monitored during all experiments. Blood samples were withdrawn from the coronary sinus to measure CSA. Injections of 5 and 10 mg of CSA in the left anterior descending coronary artery were administered to all animals and the measure of the circumflex coronary blood flow was used as control during the experiments. The decrease in left anterior descending coronary artery blood flow averaged 24 +/- 9% (p = 0.002) and 18 +/- 11% (p = 0.009), and the increase in coronary vascular resistance averaged 31 +/- 12% (p = 0.005) and 16 +/- 24% (p = 0.1) after 5 and 10 mg of CSA, respectively. There were no significant changes in circumflex coronary artery blood flow and in dP/dt during the experiments. Cyclosporine blood levels averaged 453 +/- 226 nmol/l and 1087 +/- 199 nmol/l after injections of 5 and 10 mg of CSA, respectively. In conclusion, this study suggests that CSA can cause acute vasoconstriction of the arterial coronary vasculature.