Effect of some organic acids in the incubation step on plasma renin activity

The organic acids potassium hydrogen phthalate (KHphthalate), maleic, critic, acetic, formic, and oxalic were used to adjust the pH of plasma to 5.6 +/- 0.2 in the incubation step of the procedure for the determination of plasma renin activity (PRA). When compared to the PRA determined after pH adjustment with hydrochloric acid (HCl), it was found that KHphthalate and maleic acid produced a statistically significant increase in PRA. In comparison to HCl, KHphthalate and maleic acid showed a mean percent difference of 61% and 27% respectively for a one hour incubation; and, 57% and 34% respectively for a three hour incubation.