Inter-organ Relation between Salivary Gland and Kidney in Lithium Excretion. II. Salivary, Renal and Systemic Clearances of Lithium under Continuous Stimulation of Salivation in Water Loaded Dogs

Abstract

This study was undertaken to investigate the effects of water loading on lithium clearance in dogs under the continuous stimulation of salivation as well as to clarify the mechanism of the inter-organ relation between salivary gland and kidney in lithium excretion. Dogs were given intravenously 0.145 meq/kg of lithium chloride followed by the continuous stimulation of salivation with citric acid solution. Fifty ml of water was loaded orally 7 times at 1-h intervals. Parotid and mandibular-sublingual salivas were collected separately by means of permanent fistulae. (1) Plasma concentrations of lithium were not significantly different from either those in the experiment with continuous stimulation under no water loading or those in the control experiment without continuous stimulation. (2) Salivary clearance of lithium was markedly increased compared with that in the control experiment. The urinary flow rate, which was decreased under the continuous stimulation of salivation without water loading, was restored by the water loading. The renal clearance of lithium, which was also decreased under the continuous stimulation, remained at the reduced level under the condition of this study. Consequently, the systemic clearance of lithium did not change from that in the experiment under the continuous stimulation without water loading or that in the control experiment. (3) It was suggested that the salivary and renal excretion mechanisms of lithium might be similar to those of potassium, since a similar interrelation between salivary and renal clearances was observed for potassium. (4) It was suggested that the reduction in the renal clearance of lithium under the continuous stimulation of salivation was attributed to the sodium loss caused by the excessive salivation. © 1989, The Pharmaceutical Society of Japan. All rights reserved.