Journal article

Publication year: 1998

Pages: 219-228

Journal: Acta physiologica Scandinavica

Volume number: 164

Issue number: 2

ISSN: 0001-6772

Publisher: Blackwell

Abstract: 
In order to reveal the contribution of the Na+-K+-2 Cl-- cotransporter to forskolin-induced anion secretion, the inhibition of forskolin-stimulated short-circuit current (Isc) by bumetanide, furosemide. azosemide and piretanide was investigated. In the distal colon, all blockers inhibited the forskolin-stimulated Isc with a maximal efficiency of 70%. In contrast, in the proximal colon, bumetanide and furosemide inhibited only about 40% of the forskolin response, whereas piretanide and azosemide were ineffective. A similar result was observed, when Na+ was replaced by impermeant cations suggesting especially in the proximal colon a great part of forskolin-induced anion secretion to be independent of the Na+-K+-2 Cl--cotransporter. In anion substitution experiments the forskolin-induced increase in Isc was reduced by 70-80%, if either Cl- or HCO3- were omitted from the buffer solution, whereas in the combined absence of both anions the response was nearly suppressed. Measurement of the mucosal alkalinization revealed that forskolin stimulated a HCO3- secretion, which was, however, too weak to explain the bumetanide-insensitive Isc induced by forskolin. Bumetanide inhibited the serosa-to-mucosa flux of Cl- (J(sm)(Cl)) stimulated by forskolin; an effect, which was strongly enhanced by subsequent administration of the anion exchange inhibitor, SITS. These data suggest that the bumetanide-resistant part of the forskolin-induced Isc is mainly mediated by a basolateral anion exchanger, probably a Cl--HCO3- exchanger, which contributes to forskolin-evoked Cl- secretion, and in addition by a small HCO3- secretion stimulated by the drug.

Harvard Citation style: Schultheiss, G., Hörger, S. and Diener, M. (1998) The bumetanide-resistant part of forskolin-induced anion secretion in rat colon, Acta physiologica Scandinavica, 164(2), pp. 219-228

APA Citation style: Schultheiss, G., Hörger, S., & Diener, M. (1998). The bumetanide-resistant part of forskolin-induced anion secretion in rat colon. Acta physiologica Scandinavica. 164(2), 219-228.