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Amendment history:
  • Correction (April 1993)

Research Article Free access | 10.1172/JCI116030

Microfilament-dependent activation of Na+/K+/2Cl- cotransport by cAMP in intestinal epithelial monolayers.

J B Matthews, C S Awtrey, and J L Madara

Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts.

Find articles by Matthews, J. in: PubMed | Google Scholar

Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts.

Find articles by Awtrey, C. in: PubMed | Google Scholar

Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts.

Find articles by Madara, J. in: PubMed | Google Scholar

Published October 1, 1992 - More info

Published in Volume 90, Issue 4 on October 1, 1992
J Clin Invest. 1992;90(4):1608–1613. https://doi.org/10.1172/JCI116030.
© 1992 The American Society for Clinical Investigation
Published October 1, 1992 - Version history
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Abstract

cAMP-mediated stimulation of Cl- secretion in the human intestinal cell line T84 is accompanied by significant remodeling of F-actin, and both the secretory and cytoskeletal responses may be largely ablated by previous cell loading with phalloidin derivatives, reagents that prevent dynamic reordering of microfilaments (1991. J. Clin. Invest. 87:1903-1909). In this study, we examined the effect of phalloidin loading on the cAMP-elicited activity of the individual membrane-associated transport proteins involved in electrogenic Cl- secretion. Efflux of 125I and 86Rb was used to assay forskolin-stimulated Cl- and K+ conductances, respectively, and no inhibitory effect of phalloidin could be detected. Na+/K(+)-ATPase pump activity, assessed as bumetanide-insensitive 86Rb uptake and the ability of monolayers to generate a Na+ absorptive current in response to apical addition of a Na+ ionophore, was not different between control and phalloidin-loaded monolayers. Forskolin was found to stimulate Na+/K+/2Cl- cotransport (bumetanide-sensitive 86Rb uptake) in time-dependent fashion. In the absence of any agonist, cotransporter activity was markedly decreased in phalloidin-loaded monolayers. Furthermore, under phalloidin-loaded conditions, the forskolin-elicited increase in bumetanide-sensitive 86Rb uptake was markedly attenuated. These findings suggest that cAMP-induced activity of Cl- channels, K+ channels, and the Na+/K(+)-ATPase are not influenced by F-actin stabilization. However, cAMP-induced activation of the Na+/K+/2Cl- cotransporter appears to be microfilament-dependent, and ablation of this event is likely to account for the inhibition of cAMP-elicited Cl- secretion seen in the phalloidin-loaded state. Such findings suggest that Na+/K+/2Cl- cotransporter is functionally linked to the cytoskeleton and is a regulated site of cAMP-elicited electrogenic Cl- secretion.

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