[Effects of sodium depletion in rats actively immunized against renin]

The influence of active immunization against renin on systolic blood pressure in response to a dietary sodium restriction was assessed in normotensive rats (WKY) and spontaneously hypertensive rats (SHR). Immunization was obtained by multiple injections of pure submaxillary murine renin. Animals received a normosalt diet (NS diet) for 6 days. Then sodium was abruptly removed from the diet (LS diet), and rats were maintained for an additional 6 day-period on this salt-free diet. In rats maintained on NS diet, immunization induced a decrease in systolic blood pressure (SBP) about 11 p. 100 and 27 p. 100 respectively in WKY immune and SHR immune groups. SBP was not affected by abrupt dietary sodium removal in non-immunized rats from both strains. However, in immunized rats sodium restriction was accompanied by a significant SBP decrease compared to the value observed during NS period in the same group. The relative variation in SBP was about 10 p. 100 and 14 p. 100 respectively in WKY immune and SHR immune groups. The present study shows that active immunization against renin leads to a reduction in systolic blood pressure regardless to the initial pressure level. When sodium is removed from the diet, systolic blood pressure level is maintained in non-immunized rats, whereas it decreases in immunized rats of both strains. These results confirm the importance of an efficient renin-angiotensin system in the adaptative response to sodium restriction.