A qualitative difference in plasma renin activity in Dahl rats susceptible or resistant to salt-induced hypertension

Plasma renin activity (PRA) was studied in the rats bred by Dahl for susceptibility (S-strain) or resistance (R-strain) to salt (NaCl) induced hypertension. The pH curves for PRA had different shapes. The difference in shape of the pH curves was reflected in the ratio of PRA pH 8/PRA pH 6.5. This ratio was shown to be characteristic of the strain and to be independent of changes in absolute PRA level induced by variation in dietary NaCl. The ratio of PRA pH 8/PRA pH 6.5 was also different between strains in weanling as well as adult rats. The underlying cause for the strain difference in the effect of pH on PRA is unknown, but may involve molecular differences between strains in either renin or renin substrate.