AJP - Endocrinology and Metabolism, Vol 264, Issue 1 E68-E73, Copyright © 1993 by American Physiological Society

ARTICLES

Control of electrogenic Na+ absorption in rat late distal colon by nanomolar aldosterone added in vitro

M. Fromm, J. D. Schulzke and U. Hegel
Institut fur Klinische Physiologie, Freie Universitat Berlin, Germany.

It has been possible to obtain in a mammalian epithelium of dietetically and surgically untreated animals a dose response of in vitro-added aldosterone (Aldo, 10(-10) to 10(-5) M) on electrogenic Na+ absorption (JeNa). JeNa was measured in the Ussing chamber on stripped rat late distal colon 8 h after in vitro addition of Aldo. Submaximal effects were obtained at 3 nM Aldo; after a lag time of 2 h, short-circuit current (Isc) increased to a maximum of 234 +/- 15 microA/cm2 and dropped after 0.1 mM amiloride to -18 +/- 3 microA/cm2, resulting in JeNa of 9.4 +/- 0.6 mumol.h-1 x cm-1. Net Na+ tracer fluxes and Isc exhibited parallel time courses, so that electroneutral Na+ transport was not induced in late distal colon by acute Aldo. A plot of JeNa vs. Na conductance revealed an electromotive force (ENa) of 126 +/- 1 mV for all Aldo concentrations tested. Kinetic data were as follows: Michaelis constant 1.2 nM, maximal velocity (Vmax) 10.5 mumol.h-1 x cm-2, and Hill coefficient 2.1. In contrast to the large effect in late distal colon, 3 nM Aldo caused JeNa of < 1 mumol.h-1 x cm-2 in early distal colon, proximal colon, and cecum. Antimineralocorticoid sensitivity and ENa did not vary with Aldo concentration or time of the experiment, consistent with a unique mechanism during the early and late response up to 8 h, as well as at mineralocorticoid and glucocorticoid Aldo concentrations. Acute Aldo in a range of 0.1-10 nM fully controls JeNa between zero and Vmax in late distal colon.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				M. Bertog, J. E. Cuffe, S. Pradervand, E. Hummler, A. Hartner, M. Porst, K. F. Hilgers, B. C. Rossier, and C. Korbmacher Aldosterone responsiveness of the epithelial sodium channel (ENaC) in colon is increased in a mouse model for Liddle's syndrome J. Physiol., January 15, 2008; 586(2): 459 - 475. [Abstract] [Full Text] [PDF]

				S. Vidyasagar, V. M. Rajendran, and H. J. Binder Three distinct mechanisms of HCO3- secretion in rat distal colon Am J Physiol Cell Physiol, September 1, 2004; 287(3): C612 - C621. [Abstract] [Full Text] [PDF]

				C. Barmeyer, M. Harren, H. Schmitz, U. Heinzel-Pleines, J. Mankertz, U. Seidler, I. Horak, B. Wiedenmann, M. Fromm, and J. D. Schulzke Mechanisms of diarrhea in the interleukin-2-deficient mouse model of colonic inflammation Am J Physiol Gastrointest Liver Physiol, February 1, 2004; 286(2): G244 - G252. [Abstract] [Full Text] [PDF]

				A. Inagaki, S. Yamaguchi, and T. Ishikawa Amiloride-sensitive epithelial Na+ channel currents in surface cells of rat rectal colon Am J Physiol Cell Physiol, February 1, 2004; 286(2): C380 - C390. [Abstract] [Full Text]

				A J Kroesen, M Stockmann, C Ransco, J D Schulzke, M Fromm, and H J Buhr Impairment of epithelial transport but not of barrier function in idiopathic pouchitis after ulcerative colitis Gut, June 1, 2002; 50(6): 821 - 826. [Abstract] [Full Text] [PDF]

				M. Wegmann, A. Kämpen, S. Weber, H. W. Seyberth, and A. Köckerling Effect of Hydroxyeicosatetraenoic Acids on Furosemide-Sensitive Chloride Secretion in Rat Distal Colon J. Pharmacol. Exp. Ther., October 1, 2000; 295(1): 133 - 138. [Abstract] [Full Text]

				H. J. Epple, S. Amasheh, J. Mankertz, M. Goltz, J. D. Schulzke, and M. Fromm Early aldosterone effect in distal colon by transcriptional regulation of ENaC subunits Am J Physiol Gastrointest Liver Physiol, May 1, 2000; 278(5): G718 - G724. [Abstract] [Full Text] [PDF]

				I. Grotjohann, J.-D. Schulzke, and M. Fromm Electrogenic Na+ transport in rat late distal colon by natural and synthetic glucocorticosteroids Am J Physiol Gastrointest Liver Physiol, February 1, 1999; 276(2): G491 - G498. [Abstract] [Full Text] [PDF]

				S. Watanabe, K. Matsushita, J. B. Stokes, and P. B. McCray Jr. Developmental regulation of epithelial sodium channel subunit mRNA expression in rat colon and lung Am J Physiol Gastrointest Liver Physiol, December 1, 1998; 275(6): G1227 - G1235. [Abstract] [Full Text] [PDF]