MEAL-STIMULATED CANINE JEJUNAL IONIC ABSORPTION - INFLUENCE OF MUCOSAL NEURAL BLOCKADE

The oral ingestion of a meal or the delivery of nutrients directly to the stomach or duodenum stimulates water and ion absorption from the p roximal jejunal lumen. To further investigate this phenomenon, this st udy tested two hypotheses: (I) direct jejunal nutrient delivery stimul ates jejunal absorption, and (2) the signal for jejunal absorption req uires intact enteric neurotransmission and will therefore be altered b y mucosal neural blockade with the local anesthetic bupivacaine. Intes tinal absorption studies (N = 52) were performed on eight dogs with 25 -cm jejunal Thiry-Vella fistulas (TVF) and feeding jejunostomies. Lumi nal perfusion with [C-14]PEG was used to calculate TVF absorption of H 2O, Na+, and Cl-. Six groups were randomly studied over 4 hr. Each gro up incorporated a basal hour, a TVF or jejunostomy treatment hour, and an oral (groups 1 and 3) or a jejunal (groups 4 and 6) meal stimulus. The oral and jejunal meals were isocaloric and of identical compositi on. Groups 1-3 had saline (as a control) or 0.75% bupivacaine applied to the lumen of the TVF. Groups 5 and 6 had 0.75% bupivacaine applicat ion to the feeding jejunostomy. Both the oral and the jejunal meal sti muli resulted in a significant proabsorptive response in the TVF. TVF bupivacaine reduced basal absorption but did not diminish the meal-ind uced proabsorptive response. Treatment of the jejunostomy with bupivac aine caused no change in basal or postmeal absorption in the TVF. Thes e data are consistent with the hypotheses that: (1) a proabsorptive si gnal responsible for meal-induced jejunal absorption originates from, or distal to, the jejunum, and (2) intact neural transmission maintain s the basal absorptive state of the jejunum but is not necessary for t he expression of the meal-induced proabsorptive response.