Effects of Cigarette Smoke and Nicotine on Duodenal Bicarbonate Secretion in the Rabbit and the Rat

Abstract

The effects of short-time exposure to cigarette smoke on duodenal mucosal bicarbonate secretion were studied in anesthetized rabbits and rats. The bicarbonate secretion was measured by continuous titration of recirculating luminal perfusate. In artificially ventilated rabbits, intermittent exposure to cigarette smoke during two 10-min periods caused a marked (approximately 40%) decrease (p less than 0.01) in duodenal bicarbonate secretion. After the exposures, secretion gradually recovered and had returned to the pre-exposure rate after 50 min. The decrease in secretion was associated with decreases in heart rate (approximately 15%) and blood pressure (approximately 30%) that, however, were of shorter duration. Neither reduced amounts of smoke (1/6 or 1/3) nor nicotine (25-1,000 micrograms/kg, intravenously) had any major effect on the bicarbonate secretion. In the spontaneously breathing rat, smoke was administered for 1-2 breaths every 30 s during a 5-min period. This exposure resulted in a significant (p less than 0.05) decrease in bicarbonate secretion and some increase in the blood pressure. Exposure to smoke had no effect on the secretion in rats with both splanchnic nerves cut, suggesting neural sympathetic mediation of the smoke-induced inhibition.