Renal apical membrane sodium-hydrogen exchange in genetic salt-sensitive hypertension.
Inbred Dahl/Rapp salt-sensitive and salt-resistant rats differ in their blood pressure response to dietary salt. We studied sodium-hydrogen (Na-H) exchanger kinetics in renal brush border membrane vesicles prepared from both strains on either a 1% or 8% NaCl diet. Kinetics measurements were made with the acridine orange fluorescence quenching technique in vesicles prepared at pH 6.0. The initial Na-H exchange rate was measured using preparations with similar initial quench values. The maximal transport rate (Vmax, fluorescence units per second per milligram protein [+/- SEM]) in salt-sensitive rats on a 1% NaCl diet was significantly lower than that in salt-resistant rats (36.9 +/- 4.4 versus 51.8 +/- 5.5, respectively, P < .0005). With the 8% NaCl diet for 1 week, the Vmax of salt-resistant rats decreased and became similar to that of salt-sensitive rats. The affinity for sodium (Km, millimoles per liter [+/- SEM]) was also lower in salt-sensitive rats than in salt-resistant rats while on a 1% NaCl diet (11.8 +/- 1.0 versus 19.6 +/- 2.3, respectively, P < .002). These values converged when both strains were fed an 8% NaCl diet for 1 week. Inhibition by 25 mumol/L amiloride was less in salt-sensitive rats than in salt-resistant rats on the 1% NaCl diet. These results show that salt-sensitive rats have lower renal apical membrane Na-H exchange activity than salt-resistant rats on a 1% NaCl diet.(ABSTRACT TRUNCATED AT 250 WORDS)
Lewis
J L
JL
Department of Medicine, University of Alabama at Birmingham 35294-0007.
Warnock
D G
DG
D000584:Amiloride / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004195:Disease Models, Animal; D006973:Hypertension / Q000235:genetics* / Q000378:metabolism*; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008871:Microvilli / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017673:Sodium Chloride, Dietary / Q000378:metabolism / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D017673:Sodium Chloride, Dietary; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride