JOURNAL OF PHYSIOLOGY-LONDON, vol.594, no.2, pp.357-372, 2016 (SCI-Expanded)
Knowledge on basic features of epithelial functions in the human intestine is scarce. We used Ussing chamber techniques to record basal tissue resistance (R-basal) and short circuit currents (I-SC; secretion) under basal conditions (I-SC-basal) and after electrical field stimulation (I-SC-EFS) of nerves in 2221 resectates from 435 patients. I-SC-EFS was TTX-sensitive and of comparable magnitude in the small and large intestine. I-SC-EFS or R-basal were not influenced by the patients' age, sex or disease pathologies (cancer, polyps, diverticulitis). Ion substitution, bumetanide or adenylate cyclase inhibition studies suggested that I-SC-EFS depended on epithelial cAMP-driven chloride and bicarbonate secretion but not on amiloride-sensitive sodium absorption. Although atropine-sensitive cholinergic components prevailed for I-SC-EFS of the duodenum, jejunum and ileum, PG97-269-sensitive [vasoactive intestinal peptide (VIP) receptor1 antagonist] VIPergic together with l-NAME-sensitive nitrergic components dominated the I-SC-EFS in colonic preparations. Differences in numbers of cholinergic or VIPergic neurons, sensitivity of epithelial muscarinic or VIP receptors, or stimulus frequency-dependent transmitter release were not responsible for the region-specific transmitter contribution to I-SC-EFS. Instead, the low atropine-sensitivity of I-SC-EFS in the colon was the result of high cholinesterase activity because neostigmine revealed cholinergic components. Colonic I-SC-EFS remained unchanged after tachykinin, P2X, P2Y or A1 and A2 receptor blockade. R-basal was smaller and I-SC-basal was higher in the small intestine. TTX and bumetanide decreased I-SC-basal in all regions, suggesting nerve-dependent secretory tone. I-SC-basal was atropine-sensitive in the small intestine and PG97-269-sensitive in the large intestine. This comprehensive study reveals novel insights into region-specific nerve-mediated secretion in the human small and large intestine.