Efeito genômico e não-genômico da aldosterona no trocador Na+/H+ e na H+ - ATPase no túbulo proximal (S3): papel do cálcio citosólico. / Genomic and Nongenomic Effects of Aldosterone on Na+/H+ Exchanger and H+-ATPase in Proximal Tubule (S3): role of Cytosolic Calcium.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The present study indicate that the basal pHi of proximal S3 segment is 7.10 ? 0.007 (n = 444/2117), being made the extrusion by of Na+/H+ exchanger (mainly) and H+-ATPase. Our results suggest a role for cell calcium in regulating the process of pHi recovery after the acid load induced by NH4Cl, mostly mediated by a basolateral Na+/H+ exchanger, and stimulated by Aldosterone (10-12, 10-10 e 10-8 M) and impaired by Aldosterone (10-6 M) via a genomic and nongenomic action. They are compatible with stimulation of the Na+/H+ exchanger by increases in cell calcium in the lower range (at Aldosterone 10-12 M) and inhibition at high cell calcium levels (at Aldosterone 10-6 M). The H+-ATPase is stimulated in all the used doses via a genomic and nongenomic action, this is coincident with the dose-dependent increase in [Ca2+]i. This finding is also compatible with the demonstration of a hormonal nongenomic (after 1 min or 15 min) and genomic (after 1 h) action on [Ca2+]i, on the Na+/H+ exchanger and on H+-ATPase. Our results indicating that the genomics effects are via MR receptor are in accordanc with our finding showing expression of the receptors in the proximal S3 segment of rat. These Aldosterone effects may represent physiologically relevant regulation in conditions of volume depletion or expansion in the intact animal.

ASSUNTO(S)

cálcio citosólico aldosterona h+-atpase proximal tubule h+-atpase cytosolic calcium na+/h+ exchanger trocador na+/h+ aldosterone proximal tubule

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