Natriuretic effect of acute nifedipine administration is not mediated by the renal kallikrein-kinin system

Pathophysiological Mechanisms and Correlates of Therapeutic Pharmacological Interventions in Essential Arterial Hypertension

Treating arterial hypertension (HT) remains a hard task. The hypertensive patient is often a subject with several comorbidities and metabolic abnormalities. Clinicians everyday have to choose the right drug for the single patient among the different classes of antihypertensives. Apart from lowering blood pressure, a main therapeutic target should be that of counteracting all the possible pathophysiological mechanisms involved in HT itself and in existing/potential comorbidities. All the ancillary positive and negative effects of the administered drugs should be considered: in particular, since hypertensive patients are often glucose intolerant/diabetic, carrier of serum lipids disorder, have already developed atherosclerotic diseases and endothelial dysfunction, they should not be treated with drugs negatively interfering with these conditions but with molecules that, if possible, improve them. The main pathophysiological mechanisms and correlates of therapeutic pharmacological interventions in essential HT are reviewed here.

Intracellular Ca2+ depletion and Ca2+ channel blockers increase renal kallikrein secretion

This study examined the effect of various manipulations of intracellular Ca2+ on kallikrein release by renal cortical slices. Increasing the extracellular Ca2+ concentration and the addition of Ca2+ ionophore A23187 was without effect on kallikrein release. In contrast, kallikrein release was enhanced by the addition of either extracellular or intracellular Ca2+ chelators in Ca(2+)-free medium and by two Ca2+ channel blockers, verapamil and nifedipine. Kallikrein release was also highly enhanced in depolarising medium (10-100 mM potassium chloride). Since potassium chloride induced a dose-related increase in free cytosolic Ca2+ which was abolished by nifedipine whereas the stimulation of kallikrein secretion persisted, a direct stimulating effect of potassium, at least at sub-physiological concentration, is suggested. Similarily, inhibition of either sodium/potassium-ATPase and Ca2+ ATPase by ouabain and vanadium respectively, was also without effect on kallikrein secretion. Taken together, these results indicate that intracellular Ca2+ depletion, Ca2+ channel blockers and high extracellular K+ concentrations, acting through different mechanisms, are effective stimuli for kallikrein secretion, at least in the isolated renal cortical slice.

Differential effects of nifedipine on plasma atrial natriuretic peptide in normal subjects and hypertensive patients

The physiology of atrial natriuretic peptide (ANP) secretion was studied in normotensive subjects and hypertensive patients both young and old. Basal plasma ANP concentration was least in young normotensives, intermediate in old normotensives and young hypertensives, and highest in old hypertensives. Nifedipine, a known stimulator of ANP secretion, acutely increased plasma ANP in young and old normotensive subjects but not in young hypertensive patients and half of the old hypertensive patients. Increase in serum ANP level in response to nifedipine did not augment its hypotensive effect. However, the increase of aldosterone in response to nifedipine-induced rise in plasma renin activity (PRA) seemed to be suppressed by elevated ANP.

Nitrendipine and the humoral control of sodium homeostasis

1. Nine healthy volunteers received 10 mg nitrendipine or placebo orally in random order. 2. In the subsequent 5 h urinary sodium excretion was 20% higher after nitrendipine, without any significant difference between the volume of urine excreted after nitrendipine or placebo. Mean blood pressure fell by 5 mm Hg (P less than 0.001), and mean heart rate increased by 5 beats min-1 (P less than 0.01) after nitrendipine but did not change after placebo. 3. These changes were accompanied by a significant elevation in plasma renin activity (P less than 0.001). A fall in plasma aldosterone following placebo appeared to be attenuated by nitrendipine. Plasma noradrenaline increased to a peak 3 h after nitrendipine administration (P less than 0.05) but did not change following placebo. A fall in the excretion of 6-keto PGF1 alpha following placebo was attenuated by nitrendipine. The total excretion of 6-keto PGF1 alpha after nitrendipine was significantly greater (P less than 0.05) than after placebo but not difference in the total excretion of PGE2 was detected. Nitrendipine did not affect urinary kallikrein excretion. 4. The natriuretic action of nitrendipine is not mediated by the kallikrein-kinin system, but may be related to changes in renal prostaglandins.