SUMMARY Tbe effects of potassium loading on blood pressure (BP) and the renln-angiotensin-aldosterone system were investigated in two-kidney, one clip Goldblatt hypertensive rats. Two series of experiments were performed: one was begun just after renal artery constriction, and tbe other, after hypertension had developed. Potassium loading significantly attenuated tbe development of hypertension, and was also able to abate existing renovascular hypertension. In both studies, potassium loading increased fluid intake and urine volume, which were accompanied by increased excretion of sodium and potassium. In spite of the massive diuretic effect, potassium loading significantly attenuated tbe increased plasma renin activity (PRA) induced by renal artery constriction, while it further enhanced the increased plasma aldosterone concentration (PAC) in twokidney, one clip Goldblatt hypertensive rats. There was no significant difference in the values of serum sodium and potassium between tbe two groups with or without potassium loading. These results suggest that potassium may attenuate the development of hypertension and reduce the elevated BP by diuresis and natriuresis and by suppression of the PRA in two-kidney, one clip Goldblatt hypertensive rats. "* stated that potassium has antihypertensive properties. The diuretic action of potassium had already been described in 1679, 1 and, indeed, the usefulness of Kempner's rice fruit diet for the therapy of hypertension was demonstrated.' In addition to its wellestablished diuretic effect, this substance has been reported to exert direct vasodilator effects and to attenuate vascular contractions induced by vasoactive substances.
"10 Furthermore, Douglas et al." reported that potassium is able to suppress plasma renin activity (PRA) directly.Although potassium has been accredited with these various antihypertensive effects, its precise antihypertensive mechanism still remains uncertain. In the present experiments in rats, we studied the depressor effect of potassium in established two-kidney, one clip Goldblatt hypertension and its preventive effect in the development of this type of hypertension.
Materials and MethodsMale Wistar rats, weighing 190 to 210 g, were anesthetized with ether, and the left kidney was exposed through a mid-line incision in the skin of the back; a silver clip, 0.2 mm in width, was placed on the left renal artery. All rats were maintained in humidityand temperature-controlled quarters, each rat being housed in a metabolic cage.Systolic blood pressure (BP) was measured by a tail plethysmographic method twice a week. The daily fluid intake and urine volume were measured, and the urinary excretions of sodium and potassium were determined every other day during the study. The PRA was determined by the method of Skinner, 18 and plasma aldosterone concentration (PAC) by radioimmunoassay.11 Serum and urinary electrolytes were measured with a flame photometer.Fifteen rats were killed by decapitation to obtain control values for PRA, PAC, and serum sodium and ...