Postprint version. Published in Kidney International, Volume 12, Issue 1, July 1, 1977, pages 17-20.
NOTE: At the time of publication, the author Susan C. Opava-Stitzer was affiliated with the University of Puerto Rico School of Medicine - San Juan, Puerto Rico. Currently, April 2008, she is Dean of Research and Graduate Programs at California Polytechnic State University - San Luis Obispo.
Distal nephron function of the rat during lithium chloride infusion. Chronic lithium (Li) administration in the rat leads to reduced renal concentration (TCH2O) without alterations in renal dilution (CH2O). To examine the acute effects of lithium on TCH2O and CH2O, rats were infused with a solution composed of 1% sodium chloride and 1% lithium chloride or a 0.225% lithium chloride solution at rates from 0.06 to 0.5 ml/min. In six rats, infusion of the sodium-lithium solution resulted in marked inhibition of TCH2O at any level of osmolar clearance (C0sm) when compared to animals receiving 2.2% sodium chloride alone. Administration of amiloride, 40 or 80μg/kg BW/min throughout the experiment, to ten rats infused with the sodium-lithium solution, resulted in marked improvement of TCH2O to C0sm relationship. Infusion of 0.255% lithium chloride to nine rats undergoing water diuresis led to marked reductions in CH2O as a function of distal delivery (V) when compared to rats receiving 0.225% sodium chloride alone. Infusion of amiloride did not improve the CH2O to V relationship in ten rats undergoing hypotonic lithium chloride infusion. These studies suggest that lithium interferes with sodium chloride reabsorption in the distal nephron, particularly the loop of Henle, and also reduces the permeability of the collecting duct to water. Amiloride, probably by interfering with lithium transport into collecting duct cells, corrects partially the TCH2O defect by preventing water permeability changes. The lack of effect of amiloride in CH2O studies may relate to the fact that collecting duct permeability is already at its lowest. The studies suggest that lithium ions retard chloride reabsorption in the ascending limb as inferred from the CH2O and TCH2O studies. Both chloride and sodium ions appear to be required for normal loop function.