Plasma atrial natriuretic peptide levels in elderly hypertensives: effects of blood pressure reduction with amlodipine

Atrial natriuretic peptide (ANP) is a hormone of relatively recent discovery concerned with sodium homeostasis. Increased levels of ANP are found in the elderly and in hypertensives, but the mechanisms for this are unclear. This study determined the effect of amlodipine, a calcium antagonist, which is the only class of antihypertensive agent that has little or no influence on the renin-angiotensin system (Bauer and Reams, 1988) on plasma ANP in a group of 18 elderly hypertensives and a placebo (vit B complex) on a further group of 6 elderly hypertensives. The mean pre-treatment plasma ANP was 62.7 pg/ml (range 18-148.7 pg/ml) and 52.0 pg/ml (range 15.0-148.4 pg/ml) after treatment with amlodipine (not statistically significant). However, systolic blood pressure fell from a mean of 181.6 mmHg to 151.1 mmHg and diastolic blood pressure fell from a mean of 101.6 mmHg to 83.6 mmHg after treatment with amlodipine (statistically significant, P < 0.001). In the group treated with vit B complex, the mean plasma ANP level was 68.4 pg/ml (range 31.4-119.5 pg/ml) before treatment and 63.6 pg/ml (range 29.2-127.3 pg/ml) after treatment. This was not statistically significant and there was no significant change in blood pressure. These findings reinforce the theory that raised plasma ANP levels found in elderly hypertensives are a function of the aging process itself or of age-related physiological changes rather than the result of hypertension.