Effects of nilvadipine, a new calcium entry blocker, on systemic blood pressure, cardiac hypertrophy and venous distensibility in spontaneously hypertensive rats.

We investigated the effects of three different drugs, nilvadipine (NV), nicardipine (NC) and hydralazine (HD), having calcium entry blocking and/or vasodilating properties, on blood pressure, heart weight and venous distensibility in spontaneously hypertensive rats (SHRs). All of these drugs (1.0 and/or 3.2 mg/kg/day, s.c., 12-14 weeks) countered to almost the same extent the development of hypertension in young SHRs and lowered high blood pressure in the older SHRs. In both age-groups, on the other hand, ventricular weight/body weight ratios for the NV-treated group, but not for the NC- or HD-treated group, were significantly smaller than those for the corresponding vehicle-treated group. In addition, lower body venous pressure-volume curves, which were measured on the day after the last drug administration, shifted dose-dependently in the direction of the volume for the NV-treated group, indicating that venous distensibility was expanded by NV. NC and HD did not have such an effect at the same hypotensive doses. We conclude that NV prevented the development of hypertension and lowered high blood pressure in SHRs. NV also improved cardiac hypertrophy and decreased venous capacity. The depressant effect of NV on cardiac hypertrophy may be due not only to its hypotensive effect, but also, at least partially, to its venodilating effect.