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Leite-Dellova DC, Oliveira-Souza M, Malnic G, Mello-Aires M: Genomic and nongenomic dose-dependent biphasic effect of aldosterone on Na+/H+ exchanger in proximal S3 segment: role of cytosolic calcium. Am J Physiol Renal Physiol. 2008 Nov;295(5):F1342-52. Epub 2008 Aug 20.
The effects of aldosterone on the intracellular pH recovery rate (pHirr) via Na+/H+ exchanger and on the [Ca2+] i were investigated in isolated rat S3 segment. Aldosterone [10 (-12), 10 (-10), or 10 (-8) M with 1-h, 15- or 2-min preincubation (pi)] caused a dose-dependent increase in the pHirr, but aldosterone (10 (-6) M with 1-h, 15- or 2-min pi) decreased it (these effects were prevented by HOE694 but not by S3226). After 1 min of aldosterone pi, there was a transient and dose-dependent increase of the [Ca2+] i and after 6-min pi there was a new increase of [Ca2+] i that persisted after 1 h. Spironolactone, actinomycin D, or cycloheximide did not affect the effects of aldosterone (15- or 2-min pi) but inhibited the effects of aldosterone (1-h pi) on pHirr and on [Ca2+] i. RU 486 prevented the stimulatory effect of aldosterone (10 (-12) M, 15- or 2-min pi) on both parameters and maintained the inhibitory effect of aldosterone (10 (-6) M, 15- or 2-min pi) on the pHirr but reversed its stimulatory effect on the [Ca2+] i to an inhibitory effect. The data indicate a genomic (1 h, via MR) and a nongenomic action (15 or 2 min, probably via GR) on [Ca2+] i and on the basolateral NHE1 and are compatible with stimulation of the NHE1 by increases in [Ca2+] i in the lower range (at 10 (-12) M aldosterone) and inhibition by increases at high levels (at 10 (-6) M aldosterone) or decreases in [Ca2+] i (at 10 (-6) M aldosterone plus RU 486). |
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