In vitro behavior of human intestinal mucosa. The influence of acetyl choline on ion transport.

The possibility that the autonomic nervous system may influence the function of intestinal mucosa was investigated by assessing the effect of acetyl choline on ion transport in human intestine. Isolated pieces of stripped ileal mucosa were mounted in Perspex flux-chambers and bathed in isotonic glucose Ringer's solution. Acetyl choline caused a rise in mean potential difference (8.8-12.3 mV, P less than 0.002) and short circuit current (287.7-417.2 muA-cm-2, P less than 0.01) (n = 12), observable at a concentration of 0.01 mM and maximal at 0.1 mM. This effect was enhanced by neostigmine and blocked by atropine. Isotopic flux determinations revealed a change from a small mean net Cl absorption (58) to a net Cl secretion (-4.3mueq-cm-2-h-1P less than 0.001) due predominantly to an increase in the serosal to mucosal unidirectional flux of Cl (10.63-14.35 mueq-cm-2-h-1P less than 0.05) and a smaller reduction in the mucosal to serosal flux (11.22 to 10.02 mueq-cm-2-h-1P less than 0.05). Unidirectional and net Na transport was unaffected. A similar electrical and ion transport response was observed in a single study of two pieces of jejunal mucosa. In the absence of glucose net chloride secretion was produced and again an insignificant effect on net sodium transport was noted. Acetyl choline did not provoke a sustained effect on mucosal cyclic adenine nucleotide levels although a short-lived cyclic adenine nucleotide response was seen in some tissues 20-30 s after drug addition. These studies demonstrate that acetyl choline does influence human intestinal ion transport by stimulating chloride secretion and suggest a possible mechanism by which the parasympathetic nervous system could be concerned in the control of ion transport.

Human intestinal ion transport in vitro.

The transport of sodium and chloride across human jejunal and ileal mucosa was studied using an in vitro technique. Specimens of mucosa removed at operation were stripped of muscle coats, mounted in specially designed Perspex flux chambers and bathed in warmed oxygenated and stirred buffer solutions. Evidence was obtained for the active transport of sodium in both jejunum and ileum and of chloride in the ileum. Sodium absorption was enhanced by glucose in both regions of the gut but net chloride transport was unaffected. Glucose had a greater effect on sodium transport in the ileum than the jejunum. The electrical potential difference and resistance was greater and undirectional ion fluxes smaller in jejunal than ileal mucosa. Many of these results with human intestine are similar to results reported with in vitro animal intestine. Apparent discrepancies between the behavior in vivo of human intestine and in vitro of animal intestine are thus likely to be due predominantly to technical rather species differences.