Change in plasma renin substrate in lithium-intoxicated nephrectomized rats, and the effect of sodium on plasma renin and plasma renin substrate in lithium-intoxicated rats.

Abstract

Abstract The possible effect of lithium intoxication on the synthesis of renin substrate was investigated in rats given food containing 70 mmol of lithium and 125 mmol of sodium/kg dry weight for nine days. The increase in renin substrate five hours after bilateral nephrectomy was found to be identical with the increase in control rats given no lithium. This indicates that the decrease in renin substrate seen during lithium intoxication is solely a result of the increased concentration of plasma renin. A second experiment examined whether administration of extra sodium might counteract the changes in plasma renin substrate and plasma renin that occur during lithium intoxication. In lithium–treated rats given a low–sodium diet there was a pronounced fall in renin substrate and a rise in renin as compared to the control rats. These changes were almost abolished by the administration of a high–sodium diet, but this also led to a fall in the serum lithium concentration. After administration of additional lithium, the change in renin substrate was the same as in the lithium–treated low–sodium group, and the change in renin was intermediate. The data indicate that sodium counteracts the changes in plasma renin substrate and plasma renin by increasing the renal lithium clearance, but that in addition the change in plasma renin which occurs during lithium intoxication, may be counteracted by sodium through other mechanisms.