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

Abstract

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 Ringers solution. Acetyl choline caused a rise in mean potential difference (8.8-12.3 mV, P < 0.002) and short circuit current (287.7-417.2 μA cm-2, P < 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 (+ 0.58) to a net Cl secretion (-4.3 μ eq.cm-2.h-1 P < 0.001) due predominantly to an increase in the serosal to mucosal unidirectional flux of Cl (10.63-14.35 μeq.cm-2.h-1 P < 0.05) and a smaller reduction in the mucosal to serosal flux (11.22 to 10.02 μeq.cm-2.h-1 P < 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.