title: Action of ANP on the nongenomic dose-dependent biphasic effect of aldosterone on NHE1 in proximal S3 segment.
abstract: The rapid (2 min) nongenomic effects of aldosterone (ALDO) and/or spironolactone (MR antagonist), RU 486 (GR antagonist), atrial natriuretic peptide (ANP) and dimethyl-BAPTA (BAPTA) on the intracellular pH recovery rate (pHirr) via NHE1 (basolateral Na⁺/H⁺ exchanger isoform), after the acid load induced by NH₄Cl, and on the cytosolic free calcium concentration ([Ca²⁺](i)) were investigated in the proximal S3 segment isolated from rats, by the probes BCECF-AM and FLUO-4-AM, respectively. The basal pHi was 7.15±0.008 and the basal pHirr was 0.195±0.012 pH units/min (number of tubules/number of tubular areas=16/96). Our results confirmed the rapid biphasic effect of ALDO on NHE1: ALDO (10⁻¹² M) increases the pHirr to approximately 59% of control value, and ALDO (10⁻⁶ M) decreases it to approximately 49%. Spironolactone did not change these effects, but RU 486 inhibited the stimulatory effect and maintained the inhibitory effect. ANP (10⁻⁶ M) or BAPTA (5×10⁻⁵ M) alone had no significant effect on NHE1 but prevented both effects of ALDO on this exchanger. The basal [Ca²⁺](i) was 104±3 nM (15), and ALDO (10⁻¹² or 10⁻⁶ M) increased the basal [Ca²⁺](i) to approximately 50% or 124%, respectively. RU 486, ANP and BAPTA decreased the [Ca²⁺](i) and inhibited the stimulatory effect of both doses of ALDO. The results suggest the involvement of GR on the nongenomic effects of ALDO and indicate a pHirr-regulating role for [Ca²⁺](i) that is mediated by NHE1, stimulated/impaired by ALDO, and affected by ANP or BAPTA with ALDO. The observed nongenomic hormonal interaction in the S3 segment may represent a rapid and physiologically relevant regulatory mechanism in the intact animal under conditions of volume alterations.
authors.affiliation: Department of Physiology and Biophysics, Instituto de Ciências Biomédicas, University of São Paulo, Av. Prof. Lineu Prestes, 1524, Cidade Universitária, 05508-900 SP, Brazil.
authors.forename: C
authors.initials: C
authors.lastname: Braga-Sobrinho
authors.forename: D C A
authors.initials: DC
authors.lastname: Leite-Dellova
authors.forename: M
authors.initials: M
authors.lastname: Mello-Aires
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects; D000450:Aldosterone / Q000378:metabolism*; D000643:Ammonium Chloride / Q000633:toxicity; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D042282:Microdissection; D015735:Mifepristone / Q000494:pharmacology; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013148:Spironolactone / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D000451:Mineralocorticoid Receptor Antagonists; D011965:Receptors, Glucocorticoid; C452850:Slc9a1 protein, rat; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; C472610:atrial natriuretic peptide, rat; D000643:Ammonium Chloride; D013148:Spironolactone; D015735:Mifepristone; D000450:Aldosterone; D009320:Atrial Natriuretic Factor