A DOUBLE-BLIND PLACEBO-CONTROLLED TRIAL OF THE EFFECTS OF SHORT-TERM POTASSIUM SUPPLEMENTATION ON BLOOD-PRESSURE AND ATRIAL-NATRIURETIC-PEPTIDE IN NORMOTENSIVE WOMEN

To determine the early effect of potassium loading on blood pressure regulatory mechanisms, the effect of 4 days' supplementation with 80 mmol/day KC1 on blood pressure and vasodilator hormone release was examined using a double-blind crossover design in normotensive women with a baseline potassium excretion of 51.8 +/- 2.7 mmol/day. Systolic blood pressure fell 1.7 +/- 0.6 mm Hg, (P < .01) in association with a mean increase in sodium excretion of 14.7 +/- 4.5 mmol/day and an increase in urine volume of 122.6 +/- 57.0 mL/day. There was a small but significant fall in plasma atrial natriuretic peptide (ANP) over the 4 days of potassium supplementation, while significant increases were seen in the levels of plasma potassium (P < .01) and aldosterone (P < .01). After 4 days of KC1, urinary 6-keto-PGF1-alpha was significantly elevated and correlated positively with urinary sodium excretion. Plasma renin activity was unchanged. The results suggest that increased vasodilator prostanoid synthesis and a mild natriuresis may contribute to the transient fall in systolic blood pressure. The increase in aldosterone and reduction in ANP probably represent homeostatic responses to this natriuresis, and could account for the failure of potassium supplementation to induce a long-term reduction in blood pressure in other studies in normotensive subjects.