Ba2+ inhibition of VIP-and A23187-stimulated Cl-secretion by T84 cell monolayers

KG Mandel, JA McRoberts… - … of Physiology-Cell …, 1986 - journals.physiology.org
KG Mandel, JA McRoberts, G Beuerlein, ES Foster, K Dharmsathaphorn
American Journal of Physiology-Cell Physiology, 1986journals.physiology.org
Addition of either 10 (-8) M vasoactive intestinal polypeptide (VIP) or 10 (-6) M A23187 to
T84 cell monolayers, grown on permeable supports and mounted in Ussing chambers,
stimulated net Cl-secretion. The effect of 10 (-6) M A23187 on Cl-flux was consistently
smaller than that observed with 10 (-8) M VIP. In both cases the increase in net Cl-secretion
accounted for the entire change in the observed short-circuit current (Isc). Since Cl-enters
the cells through a basolaterally localized Na+-K+-Cl (-)-cotransport system (J. Clin. Invest …
Addition of either 10(-8) M vasoactive intestinal polypeptide (VIP) or 10(-6) M A23187 to T84 cell monolayers, grown on permeable supports and mounted in Ussing chambers, stimulated net Cl- secretion. The effect of 10(-6) M A23187 on Cl- flux was consistently smaller than that observed with 10(-8) M VIP. In both cases the increase in net Cl- secretion accounted for the entire change in the observed short-circuit current (Isc). Since Cl- enters the cells through a basolaterally localized Na+-K+-Cl(-)-cotransport system (J. Clin. Invest. 75: 462, 1985), the fate of K+, which is cotransported with Cl- during VIP, and A23187-mediated Cl- secretion was explored. Unidirectional and net transepithelial 42K+ flux rates were negligible compared with 36Cl- flux rates (less than 4% of Cl- flux), indicating that little K+ was secreted along with Cl-. K+ recycling across the basolateral membrane was suggested from experiments in which 86Rb+ efflux (as a tracer for K+) was measured across the apical and basolateral membranes of 86Rb+ -preloaded monolayers under voltage-clamped conditions. In the absence of secretagogues, 86Rb+ efflux was 10-fold higher across the basolateral membrane than across the apical membrane. 86Rb+ efflux across the basolateral membrane was accelerated two- to threefold by addition of either VIP or A23187. In each case accelerated efflux was inhibited by 5 mM Ba2+. Cl- secretion induced by VIP or A23187 was also inhibited by serosal addition of Ba2+.(ABSTRACT TRUNCATED AT 250 WORDS)
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