1. We examined preproendothelin-1, ET(A) and ET(B) receptor mRNA levels in aortic endothelial and smooth muscle cells from cyclosporine (CyA)-induced hypertensive rats using the reverse transcription polymerase chain reaction method, 2. Aortic endothelial preproendothelin-1 mRNA expression was about 1.5-fold higher, while that of ET(B) receptor mRNA was markedly decreased in CgA-treated rats compared with those in controls. 3. The expression of ET(A) receptor mRNA in smooth muscle cells from CyA-induced hypertensive rats was increased about two-fold over that in cells from control animals. 4. Thus, increased endothelial preproendothelin-1, and ET(A) receptor mRNA levels in smooth muscle cells, which are concomitant with the decrease in ET(B) receptor mRNA levels in endothelium, mag contribute to CyA-induced hypertension in rats.