Effect of a calcium entry blocker on blood pressure, plasma renin activity, aldosterone and catecholamines in normotensive subjects

Differential effects of antihypertensive drugs on neurohormonal activation: insights from a population-based sample

OBJECTIVES

The clinical course of hypertension or heart failure may be modified by the extent of concurrent neurohormonal activation. Factors that regulate neurohormones in patients with these conditions are complex. In the present study, we examined the relative contribution of antihypertensive therapy to the variability of neurohormonal levels in a well defined population based sample.

DESIGN AND SETTING

Cross-sectional study of a mixed urban and rural population.

SUBJECTS

Middle-aged individuals (n = 646) were analysed in order to elucidate determinants of neurohormone levels by uni- and multivariate comparisons. The assessment included anthropometric, echocardiographic and, if appropriate, genotype information.

RESULTS

The intake of antihypertensive drugs was related to significant alterations of neurohormone levels that, in part, exceeded the contribution of all other variables studied. Multivariate analyses revealed that renin levels were independently related to the intake of beta blockers (n = 80; -8.4 mU L-1; P = 0.001), angiotensin-converting enzyme (ACE)-inhibitors (n = 39; +15.9 mU L-1; P = 0.0001), diuretics (n = 62; +14.3 mU L-1; P = 0.0001), and calcium channel blockers (n = 45; +5.9 mU L-1; P = 0.05). Aldosterone levels were related to ACE-inhibition (-156.5 pmol L-1; P = 0.04) and diuretic treatment (+422.4 pmol L-1; P = 0.0001) in an opposite fashion whereas beta blockers and calcium channel blockers had no significant independent effects. The levels of the atrial natriuretic peptide were significantly related to the use of beta blockers (+3.9 pmol L-1; P = 0.002) and calcium channel blockers (+3.1 pmol L-1; P = 0.05). Finally, serum angiotensinogen levels and ACE activity were not found to be significantly affected by antihypertensive medication but were rather related to gender or genotype.

CONCLUSIONS

The data emphasize that antihypertensive treatment with different classes of drugs may modulate serum levels of neurohormones substantially resulting in distinct patterns of activation. These drug-related effects may require consideration when neurohormonal activation is of functional relevance or when neurohormones serve as prognostic predictors in patients with cardiovascular disorders.

Effect of L-dopa in young patients with hypertension

The effects of L-dopa on blood pressure, heart rate, plasma renin activity, norepinephrine, epinephrine and prolactin were studied in a randomized single-blind trial in 36 patients with essential hypertension. In response to L-dopa, 250 mg administered orally, the blood pressure decreased significantly as compared with the results of placebo treatment. The heart rate and plasma norepinephrine and epinephrine were unchanged. The plasma renin activity and prolactin decreased as a result of L-dopa administration. The administration of a peripheral DA2 dopamine receptor blocker, domperidone (20 mg, orally) prevented the L-dopa-induced reduction in plasma prolactin but failed to block the fall in blood pressure and plasma renin activity. These results suggest that the blood pressure-lowering effect of L-dopa may be mediated through multiple sites involving D1 dopamine receptors, the central nervous system, and the renin-angiotensin system.

Effect of captopril on plasma prolactin in patients with essential hypertension

The effects of the angiotensin-converting enzyme inhibitor captopril on blood pressure, heart rate, plasma prolactin, and renin activity were examined in a single-blind, placebo-controlled trial on 30 patients with essential hypertension (15 given drug, 15 placebo). Captopril, 25 mg administered orally, reduced the blood pressure and increased the plasma renin activity. Captopril decreased mean plasma prolactin from 17.5 +/- 1.4 ng/mL to 9.1 +/- 1.0 ng/mL (p less than 0.001). Significant correlation was found between captopril-induced change from control values of plasma prolactin (delta plasma prolactin) vs delta plasma renin activity (r = -0.688, p less than 0.001). These results suggest that acute administration of captopril was accompanied by a reduction in plasma prolactin and that this reduction may be of clinical significance during therapy of hypertension.

Effects of nicardipine on blood pressure and renal function in elderly hypertensive patients with renal dysfunction

The effects of monotherapy with nicardipine, 20 mg three times a day, have been investigated in a 1-year study of 26 elderly (greater than 60 years) patients with hypertension with various types of renal dysfunction and seven without renal dysfunction. Parameters measured included blood pressure, blood chemistry (serum creatinine, uric acid, blood urea nitrogen, blood glucose total cholesterol, and electrolytes), plasma renin activity, and plasma aldosterone concentration. Nicardipine was effective in reducing blood pressure in all patients with diabetic nephropathy, parenchymal renal diseases, or hypertensive nephropathy, and in those without renal dysfunction. Serum creatinine and blood urea nitrogen levels were slightly elevated in some patients whose pretreatment serum creatinine level was greater than 2 mg/dl, regardless of the type of nephropathy. However, it was not determined whether this effect was the result of a reduction in blood pressure induced by nicardipine. Serum sodium, potassium, total cholesterol, and blood glucose levels were unchanged by the administration of nicardipine. Changes in plasma renin activity and aldosterone levels were not significant. These results suggest that nicardipine can be used safely in elderly patients with hypertension with renal dysfunction, regardless of the type of nephropathy.

Nicardipine causes sympathetic activation that does not involve baroreceptor reflex tachycardia in conscious sinoaortic-denervated dogs

Nicardipine-induced tachycardia is generally attributed to the involvement of the baroreflex. The effects of nicardipine on blood pressure (BP) and heart rate (HR) as well as on plasma catecholamine levels were studied in six conscious dogs made hypertensive by sinoaortic denervation. Nicardipine (50, 100 and 200 micrograms/kg i.v.) induced both a significant decrease in mean BP and a marked increase in HR in these dogs whereas the catecholamines rose significantly. Nicardipine-induced tachycardia cannot be explained by a baroreflex mechanism only. It is suggested that nicardipine induces an increase in HR and sympathetic tone, probably by a direct action on central cardiovascular mechanisms.