Cyclosporin A-induced coronary artery vasoconstriction through myogenic and endothelium-dependent mechanisms

The exact mechanism of vascular toxicity of cyclosporin A (CSA) remains unknown. It has been reported that an impairment of endothelium-mediated vascular reactivity may be involved.

We studied the response to intracoronary injections of acetylcholine (ACh) (30 ng/kg), adenosine (100 ng/kg), and nitroglycerin (NTG) (1.7 micrograms/kg) before and after intracoronary infusion of CSA (20 mg over 20 minutes) and of L-arginine (10 mg.kg-1.min-1). Experiments were performed on 11 open-chest dogs anesthetized and instrumented for measurements of coronary blood flow (CBF) in the left anterior descending (LAD) and left circumflex (LCx) coronary arteries, left ventricular dP/dt, mean aortic pressure, and coronary sinus pressure. CSA, L-arginine, ACh, adenosine, and NTG were injected into the LAD, and the LCx served as control. The increase in CBF in the LAD with ACh administration averaged 21 +/- 11 mL/min before CSA, 15 +/- 10 mL/min after CSA, and 15 +/- 8 mL/min during L-arginine injection (P = .2). Adenosine caused an increase in CBF in the LAD averaging 20 +/- 10 mL/min before CSA, 10 +/- 8 mL/min after CSA, and 17 +/- 12 mL/min during L-arginine injection (P = .004). NTG caused an increase in CBF in the LAD averaging 21 +/- 10 mL/min before CSA, 13 +/- 11 mL/min after CSA, and 14 +/- 7 after administration of L-arginine (P = .009).

These results suggest that direct intracoronary injection of CSA induces a vasoconstrictive response through endothelium-dependent and myogenic mechanisms. The muscarinic endothelial response was not affected by CSA, whereas the purinergic action of CSA was restored after L-arginine administration.