Inter-organ relation between salivary gland and kidney in lithium excretion. III. Enhanced salivary and systemic clearance of Li+ by oral administration of NaCl in dogs.

Effects of oral administration of NaCl on salivary and systemic clearance of Li+ were investigated following bolus intravenous administration of LiCl in male beagle dogs. Fifty ml of NaCl solution (100 meq/l) was administered orally 7 times at 1 h intervals. Gustatory stimulation of salivation was continued for 390 min using citric acid solution. Saliva was collected by means of permanent fistulae for parotid and mandibular-sublingual glands. Salivary clearance of Li+ was markedly increased by continuous stimulation of salivation, and was enhanced further after oral administration of NaCl solution. Renal clearance of Li+ showed a decreasing tendency under continuous salivation compared with the condition without gustatory stimulation; however, this decreasing tendency disappeared after oral administration of NaCl solution. Consequently, systemic clearance of Li+ was increased due to the contribution of increased salivary clearance. Enhancement of salivary Li+ clearance after administration of NaCl suggests the salivary excretion mechanism of Li+ may include a reabsorption process, like its renal excretion. Administration of NaCl solution had similar effects on salivary and systemic clearances of K+ to those on Li+ clearances, and a significant correlation was observed between Li+ and K+ clearances of both salivary gland and kidney.