The reactivity of peripheral vessels of normo- and hypertensives

The effect of calcium antagonist nifedipine (N) was studied in the changes of blood pressure, total peripheral resistance, activity of the transport membrane ATPase of erythrocyte ghosts, the plasma level of digitalis-like factor and the plasma renin activity. The studies were performed in 10 healthy volunteers and in 19 hypertensive patients after the intake of a single dose of 20 mg N. The changes were studied in the hypertensives after the intake of the drug in daily doses of 3 times 10 mg over 4 weeks, too. The systolic and diastolic blood pressure and peripheral resistance of the forearm decreased in hypertensives after a single dose of nifedipine as well as after the treatment with 30 mg daily over 4 weeks (170.8/109.5 vs 145.3/98.3 mmHg). As compared with the membrane ATPase activity of normotensives, that of the hypertensives was distinctly depressed (0.403 vs 0.321 mumol P(i).mg-1.h-1; p less than 0.01), while after N treatment, the enzyme activity increased to values of those of the normotensives 0.403 mumol P(i).mg-1.h-1). The mean peripheral resistance was not significantly depressed after the long-term treatment with N (2,085 vs 1,535 dyn.s-1.cm-5), while in several hypertensives (9 of 19) a distinct reduction was measured. Analogous results were found in case of the mean renin activity and the activity of several hypertensives after the N treatment. The N effect on the membrane ATPase system is discussed in connection with the hypothesis of Blaustein [1977] (Na(+)- with consecutive Ca(2+)-overload of the cell) and a possible influence of the drug on the electrolyte transport via membrane.