The effects of chronic ethanol administration on stimulated parotid secretion in the rat

Young adult male rats were maintained on a regimen of twice daily intragastric administration of 4 ml of 35% (v/v) ethanol in water (daily dose approximately 7.0 g/kg) or 4 ml of calorifically equivalent sucrose solution over approximately 100 days. A second control group received no intragastric solutions. Under Valium-Hypnorm anaesthesia, parotid saliva was collected by intra-oral duct cannulation following stimulation by pilocarpine (10 mg/kg, subcutaneously) or by isoprenaline (30 mg/kg s.c.). In the ethanol-dosed rats the initial parotid salivary flow rate was raised in comparison to control animals by 39% after pilocarpine stimulation and by 37% after isoprenaline stimulation. The protein concentration was significantly reduced in saliva from ethanol-dosed rats compared to control groups but the amylase activity per ml of saliva was not significantly different from control groups. After pilocarpine stimulation, the [K+] was significantly higher in ethanol-dosed rats than in controls, but the [Na+] was effectively lower (allowing for flow rate differences). The blood-ethanol level was zero at the time of collection of saliva, suggesting that the salivary differences are due to functional adaptation induced in acinar and ductal epithelia by prolonged repeated exposure to high doses of ethanol.