Nifedipine and diltiazem but not verapamil up-regulate endothelial nitric-oxide synthase expression.

We have recently shown that felodipine, a long-acting dihydropyridine L-type calcium channel blocker (CCB), up-regulates nitric oxide (NO) production and endothelial NO synthase (eNOS) expression and activity in cultured endothelial cells as well as in animals with chronic renal failure. This study was intended to compare the effects of prototypes of the three classes of L-type CCBs on the NO system in cultured human coronary artery endothelial cells. Thus, cultured endothelial cells were incubated either with nifedipine, diltiazem, or verapamil for 24 h at 10(-5) to 10(-7) M concentrations. Cells incubated with inactive vehicle served as controls. NO production, as discerned from total nitrate plus nitrite recovered in the medium, was significantly increased by nifedipine (P <.03) and by diltiazem (P <.05). However, NO production remained unchanged with verapamil (P = NS). Similarly, eNOS protein abundance was increased significantly by nifedipine (P <.05) and diltiazem (P <.05). In contrast, eNOS expression was not changed by verapamil (P = NS). Likewise, NOS activity, as measured from [(3)H]L-arginine to [(3)H]L-citrulline conversion, significantly increased with nifedipine (P <.01) and diltiazem (P <.01). However, incubation with verapamil failed to alter NOS activity of the cultured endothelial cells (P = NS). We concluded that prototypes of dihydropyridine and benzothiazepine classes, but not phenylalkylamine class of CCBs, up-regulate the NO system. This may, in part, account for the different biological properties of these agents.