tokens: To clarify the mechanisms of FK 506 - induced hypertension , we studied the chronic effects of FK 506 on the synthesis of endothelin - 1 ( ET - 1 ) , the expression of mRNA of ET - 1 and endothelin - converting enzyme - 1 ( ECE - 1 ) , the endothelial nitric oxide synthase ( eNOS ) activity , and the expression of mRNA of eNOS and C - type natriuretic peptide ( CNP ) in rat blood vessels .