Antihypertensive effects of m-nisoldipine and nisoldipine on conscious renal hypertensive rats and dogs

The antihypertensive effects of m-nisoldipine (m-Nis) and nisoldipine (Nis) by ig 0.3, 1.0, 3.0 and 1.0, 3.0, 9.0 mg.kg-1 respectively on renal hypertensive rats (RHR) and 0.1, 0.3, 1.0 mg.kg-1 orally (for both drugs) on renal hypertensive dogs (RHD) were studied. Both m-Nis and Nis depressed blood pressure (BP) dose-dependently in RHR and RHD. The reduction of blood pressure correlated well with the m-Nis concentration in plasma of RHD. On the basis of ED20 (HR)/ED20 (BP), the hypotensive effect of m-Nis on systolic blood pressure (SBP) was only 1.6 times as great as that of Nis on RHR (P less than 0.05), but in RHD, both drugs showed the same potency (P greater than 0.05). In both models, m-Nis showed much more potent effect on diastolic blood pressure (DBP) than Nis (P less than 0.01), and possessed stronger hypotensive effects on DBP than on SBP (P less than 0.05 and P less than 0.01); but for Nis, its effects on SBP and DBP appeared to be in the same order (P greater than 0.05). The fall in BP was accompanied by a transient increase of heart rates (HR) with m-Nis and Nis in RHR and RHD. The chronic antihypertensive effects of m-Nis and Nis were also remarkable with 1.0 mg.kg-1 daily at 9 AM for 21 d. During this period, the BP and HR lowered to nearly normal level. After withdrawal of m-Nis and Nis, the hypotensive effects lasted nearly 1 wk.