Differential aldosterone effects on two epithelial cell pools of [3H]ouabain binding sites
The A6 cell line, derived from the kidney of Xenopus laevis has earlier been shown to respond to aldosterone with an increase in the rate of Na+ transport across the epithelium (8). The rate-limiting steps for transcellular Na+ transport are the passive flux of Na+ into the cytoplasm through amiloride-sensitive Na+-channels in the apical membrane, and the active extrusion of Na+ by Na+/K+-pumps in the basolateral membrane (4). Aldosterone is believed to augment the transcellular Na+ transport by a two-step process. In the early or acute aldosterone-induced response, the molecular activity of existing Na+/K+-pumps in the basolateral membrane is increased in response to an upregulation of the apical membrane Na+ conductance (1), whereas the late or chronic phase of aldosterone action involves upregulation of the amount of Na+/K+-pump sites in the basolateral membrane (3,4).
KeywordsCellulose Sucrose Filtration Penicillin Vanadate
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- 7.Pellanda AM, Gaeggeler HP, Horisberger JD, Rossier BC (1992) Am J Physiol 262: C899–C906Google Scholar