| Abstract: | Lithium inhibits the catecholamine-dependent cyclic adenosine monophosphate (AMP) generation in the kidney but not the hemodynamic effects of beta-adrenergic stimulation. Therefore, the possible role of catecholamine-dependent cyclic AMP in the release of renin was investigated in lithium-treated dogs both in vivo and vitro. Lithium therapy had no measurable effect on the increase in plasma renin activity induced by an injection of isoproterenol (2.6 plus and minus 1.2 (SE) ng/hour in control dogs vs. 3.0 plus and minus 1.2 ng/hour in lithium-treated dogs, P greater than 0.05). However, lithium inhibited the isoproterenol-induced increase in urinary excretion of cyclic AMP in vivo (791 plus and minus 199 pmoles/min in control dogs vs. 123 plus and minus 129 pmoles/min in lithium-treated dogs, P less than 0.05) and the increase in cyclic AMP concentration in renal tissue in vitro (4.50 plus and minus 0.15 pmoles/ng wet tissue in control dogs vs. 0.34 plus and minus 0.26 pmoles/mg in lithium-treated dogs, P less than 0.01). The finding that, in the lithium-treated dogs, isoproternol increased plasma renin activity but not cyclic AMP generation in the kidney suggests that the increase in plasma renin activity observed after an injection of isoproterenol is probably not mediated through the beta-adrenergic stimulus-dependent cyclic AMP system in the kidney. |
