Author: Wehling, Martin

Source: Heart Failure Reviews, Volume 10, Number 1, January 2005 , pp. 39-46(8)

Publisher: Springer

Abstract:

Genomic mechanisms of mineralocorticoid action have been increasingly elucidated over the past four decades. In renal epithelia, the main effect is an increase in sodium transport through activation and de novo synthesis of epithelial sodium channels. This leads to increased concentrations of intracellular sodium activating sodium-potassium-ATPase molecules mainly at the basolateral membrane which extrude sodium back into the blood stream. In contrast, rapid steroid actions have been widely recognized only recently. The present article summarizes both traditional and rapid effects of mineralocorticoid hormones on intracellular electrolytes, e.g. free intracellular calcium in vascular smooth muscle cells as determined by fura 2 spectrofluorometry in single cultured cells from rat aorta. Latter effects are almost immediate, reach a plateau after only 3 to 5 minutes and are characterized by high specificity for mineralocorticoids versus glucocorticoids. The effect of aldosterone is blocked by neomycin and short-term treatment with phorbol esters but augmented by staurosporine, indicating an involvement of phospholipase C and protein kinase C. The Ca²⁺ effect appears to involve the release of intracellular Ca²⁺, as shown by the inhibitory effect of thapsigargin. This mechanism operates at physiological subnanomolar aldosterone concentrations and appears to result in rapid fine tuning of cardiovascular responsivity.

As a landmark feature of these rapid effects, insensitivity to classic antimineralocorticosteroids, e.g. spironolactone or canrenone has been found in the majority of observations. In an integrated view, mineralocorticoids seem to mainly effect intracellular electrolytes genomically to induce transepithelial transport, and induce nongenomically mediated alterations of cell function (e.g. vasoconstriction) by rapid effects on intracellular electrolytes such as free intracellular calcium.

Keywords: mineralocorticoids; intracellular electrolytes; rapid effects; second messengers

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s10741-005-2347-z

Affiliations: 1: Institute of Clinical Pharmacology, Faculty for Clinical Medicine at Mannheim, University of Heidelberg, 68167 Mannheim, Germany/AstraZeneca R&D, Mölndal, Sweden, Email: martin.wehling@kpha.ma.uni-heidelberg.de

Publication date: 2005-01-01

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