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  • Title: Effects of secretagogues on the K+ permeability of mucosal and serosal borders of rabbit colonic mucosa.
    Author: Moreto M, Planas JM, Naftalin RJ.
    Journal: Biochim Biophys Acta; 1981 Nov 06; 648(2):215-24. PubMed ID: 6272851.
    Abstract:
    (1) K+ efflux rates from the mucosal and serosal surfaces of sheets of rabbit colonic mucosa have been determined by measuring net K+ loss into K+-free Ringer solution bathing each side of the tissue. (2) Initially, there is a high rate of K+ loss from the tissue, this falls to a lower steady-state rate after 20 min. Loss of K+ from the tissue into the serosal bath is 6-8 fold faster than loss to the mucosal bath. (3) A number of intestinal secretagogues, e.g. theophylline, cyclic AMP, carbachol, ionophore A23187, as well as the laxative bisacodyl, raise the K+ efflux rate across the mucosal border by 200-300%. In the case of K+ efflux induced by carbachol the effect is shown to be dependent on raised levels of intracellular Ca2+. Ca2+-calmodulin complex does not appear to be be involved in activation of K+ efflux across the mucosal border. (4) Amiloride does not block mucosal K+ efflux, but tetraethyl-ammonium does inhibit K+ efflux across the mucosal border, induced by either bisacodyl or raised intracellular Ca2+. (5) The results suggest that laxatives may increase the rate of K+ secretion into the colonic lumen by raising the K+ permeability of the mucosal border.
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