| Abstract: | Abstract. In the control subject, plasma angiotensin production is a linear function of plasma renin content. Upon incubation of this same plasma in the presence of an excess of homologous renin, angiotensin production is finally limited by the plasma content of renin substrate (PRS). By this method, PRS levels were measured and compared with levels of plasma renin activity (PRA), urinary aldosterone excretion, and sweat sodium and potassium content, in sixteen normal human subjects, aged twenty-five to thirty years, under three defined metabolic conditions: unrestricted sodium intake, salt depletion, constant sodium intake plus administration of desoxycorticosterone acetate (DOCA). 1) Unrestricted Sodium Intake. In these control subjects, in perfect health, there exist important individual differences in PRS levels. The PRS levels seem to be quite constant for a given subject under a given metabolic condition: the levels remained the same after a four month interval for a given subject. 2) Salt Depletion. Activation of the renin-angiotensinaldosterone system (RAAS), as shown by an elevation of PRA and of urinary aldosterone excretion, is accompanied by a decrease in PRS levels. 3) Constant Sodium Intake Plus Administration of DOCA. Inactivation of the RAAS, as shown by lowering of PRA and of urinary aldosterone excretion, is accompanied by a marked elevation of PRS levels. It would appear that, in human control subjects there exists an inverse relationship between PRS and PRA levels. |
