Acta Physiologica 2005; Volume 185, Supplement 649
Belgian Society for Fundamental and Clinical Physiology and Pharmacology, Autumn Meeting 2005
MEMBRANE CHOLESTEROL EXTRACTION ATTENUATES NA+ TRANSPORT ACTIVATION IN A6 RENAL EPITHELIA
Abstract number: ORAL-9
Jans D., Balut C., Steels P., Van Driessche W.
Hasselt University, Laboratory of Physiology, Agoralaan 1D, B-3590-Diepenbeek (Belgium)
We investigated the role of the membrane cholesterol content on the regulation of Na+ transport activation in A6 renal epithelia. Voltage-clamped epithelia were continuously monitored for changes in short-circuit current (Isc), transepithelial conductance (GT) and capacitance (CT). Cholesterol was extracted from either the apical or the basolateral membranes by local perfusion with methyl-b-cyclodextrin (mbCD, 10 mM) for 1 h. Subsequently, Na+ transport was activated by applying adenosine (1 mM) to the basolateral border. Apical membrane cholesterol extraction did not affect the basal levels of Na+ transport, but attenuated the increase in amiloride-sensitive Isc elicited by basolateral adenosine with 47%. The reduced levels of cholesterol in the apical membrane did not affect the 10% rise in CT, pointing to an intact process of channel insertion. Analysis of the fluctuation in current induced by 6-chloro-3,5-diaminopyrazine-2-carboxamide (CDPC) revealed a decrease in Na+ channel open probability (ENaC Po) at the apical membrane, whereas the number of Na+ conducting channels approximately doubled in both conditions. Basolateral membrane cholesterol extraction already reduced the basal levels of Na+ transport. In addition, the reduced basolateral membrane cholesterol content completely abolished the activation of Na+ transport in response to a hyposmotic shock. Impedance analysis revealed that basolateral membrane cholesterol extraction reduced the activity of the Na+/K+-ATPase. Interestingly, cholesterol extraction from the basolateral membrane did not affect the regulatory volume decrease, indicating that transporters involved in volume regulation were still intact in these conditions.
To cite this abstract, please use the following information:
Acta Physiologica 2005; Volume 185, Supplement 649 :ORAL-9