Inhibition by lithium of gentamicin-induced release of N-acetyl-beta-D-glucosaminidase in rat submandibular saliva.

1. The effects of gentamicin, lithium and concurrent treatment of these drugs on concentration of total protein and activity of the enzyme N-acetyl-beta-D-glucosaminidase (NAG) in rat submandibular saliva were studied. 2. Pure submandibular saliva was collected intraorally by micropolyethylene canula from anesthetized rats with the use of pilocarpine as secretagogue. 3. Daily intraperitoneal injection of gentamicin (50 mg kg/day) for 5 consecutive days caused a marked increase in total protein concentration and the NAG activity. 4. Chronic treatment of rats for 10 days with lithium chloride solution (1,200 mg/l) caused a significant decrease in total protein concentration but did not affect the NAG activity. 5. Concurrent treatment of lithium with gentamicin caused the total protein concentration and the NAG activity of submandibular saliva to reach to those of controls. 6. In this regard, the protective effects of lithium may be due to interference of this ion with the phosphoinositide cycle.