Failure of NaHCO, and KHCO, to inhibit renin in the rat

KOTCHEN,THEODORE A., JOHN H. GALLA, AND ROBERT G. LUKE. Failure of NaHCO, and KHCO, to inhibit renin in the rat. Am. J. Physiol. 231(4): 1050-1056. 1976. -To evaluate the contribution of chloride to NaCland KCl-induced renin inhibition, renin responses to NaCl or NaHCO, and to KC1 or KHCO, loading were compared in NaCl-deprived rats. Sodium balance in animals drinking isotonic NaHCO, and NaCl for 9 days did not differ (P> 0.40); K+ balance was less positive in NaHCO,-drinking animals (P < 0.005). Plasma renin activity (PRA) in NaCl-loaded (16.5 rig/ml per h * 4.4 SE), but not in NaHCO,-loaded rats (57.2 t 9.8), was lower (P < 0.005) than in NaCl-deprived controls (44.8 IL 4.7). Renal renin content (RRC) of NaCl but not of NaHCO,-drinking animals was also decreased (P < 0.02). Both PRA and RRC of KClbut not of KHCO,-loaded rats (5 meq K+/lO g diet) were lower (P < 0.01) than in NaCl-deprived controls. After acute intravenous expansion with isotonic NaCl or NaHCO,, increases of plasma volume and plasma K+ did not differ (P > 0.05). However, PRA of NaCl-expanded rats (11.8 * 3.8) was lower (P < 0.05) than in NaHCO,-expanded animals (29.7 * 8.5). The failure of NaHCO, and KHCO, to inhibit renin suggests a role for chloride in mediating the renin responses to Na+ and K+.