Absence of a renin-angiotensin-aldosterone axis contribution to basel blood pressure differences between borderline hypertensive and Wistar-Kyoto rats

Systolic arterial blood pressures of F₁ (155 mm Hg) and WKY (130 mm Hg) rats are invariant at 14 through 45 weeks of age (Lawler, et al., Fed. Proc. 40 (#3), 528). At 14 and 28 weeks, significant differences in four renal-adrenal parameters are present: plasma renin activity (PRA), plasma angiotensin-1 concentration (A-1), plasma Na⁺ concentration, and plasma aldosterone concentration. At 45 weeks, strain differences in these parameters are absent. Since only static measurements of these renal-adrenal parameters were made, capacitance differences in these parameters between strains were sought. Unstimulated rates of aldosterone synthesis by adrenal cortices in vitro, and the effects on PRA of exogenous A-11 and angiotensinogen were therefore determined at 45 weeks for both F₁ and WKY rats. No strain specific differences in parameter capacity or regulation by A-II angiotensinogen were noted. We conclude that strain specific differences in these renal-adrenal parameters to chronic systolic arterial blood pressure differences are compensatory rather than contributory in nature at 14 and 28 weeks, becoming refractory to the systolic differences by 45 weeks of age. (Supported in part by USPHS. NIH Grants HL #19680 and Al #12779).