Potentiation of vascular smooth muscle cell activity by cyclosporin A.

Pretreatment of rat vascular smooth muscle cells with cyclosporin A caused concentration- and time-dependent enhancement of both angiotensin II- and platelet-derived growth factor-stimulated cellular functions, which may be related to a rise in vascular tone. In particular, cyclosporin A increased cytosolic free calcium, and augmented the agonist-induced formation of inositol polyphosphate. In addition, it markedly increased the sensitivity of the cells to platelet-derived growth factor-mediated stimulation of thymidine incorporation. The potentiation of vascular smooth muscle cell activity by cyclosporin A may be a novel mechanism by which it exerts an adverse vasoconstrictor effect.