Rubidium absorption and proton secretion by rabbit outer medullary collecting duct via H-K-ATPase.
Multiple lines of evidence support the hypothesis that the outer medullary collecting duct from the inner stripe (OMCDi) possesses a functional proton-potassium-activated adenosinetriphosphatase (H-K-ATPase). To examine the effect of inhibition of H-K-ATPase on Rb efflux, we measured the Rb tracer rate efflux coefficient (KRb) across the OMCDi of animals adapted to a K-restricted diet using the selective K-competitive H-K-ATPase inhibitor, Sch 28080. Sch 28080 (10 microM) did not significantly alter transepithelial voltage (VT) but significantly decreased KRb by 41%. We further examined the effect of 10% peritubular CO2 on KRb and the subsequent effect of Sch 28080 (10 microM) on KRb. After exposure to 10% CO2 for 120 min, vehicle-treated tubules exhibited a small but significant increase in KRb without a significant change in VT. In contrast, 10 microM Sch 28080 significantly decreased KRb by 44% without affecting VT. The lack of an effect of H-K-ATPase inhibition on VT in the presence of either 5% or 10% CO2 was in marked contrast to the effect of carbonic anhydrase inhibition (CAI). CAI consistently and significantly decreased VT either in the presence of 5% or 10% CO2. To address whether H-K-ATPase also participates in proton secretion we examined the effect of Sch 28080 (10 microM) on net bicarbonate absorption by the OMCDi of rabbits fed a normal rabbit ration and rabbits adapted to a K-restricted diet.(ABSTRACT TRUNCATED AT 250 WORDS)
Wingo
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Laboratory of Epithelial Transport, University of Florida, Gainesville.
Armitage
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D000042:Absorption; D000143:Acids / Q000037:antagonists & inhibitors; D000818:Animals; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D004594:Electrophysiology; D004848:Epithelium / Q000502:physiology; D005260:Female; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D007679:Kidney Medulla; D007685:Kidney Tubules, Collecting / Q000378:metabolism* / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D054328:Proton Pump Inhibitors; D011522:Protons; D011817:Rabbits; D012413:Rubidium / Q000493:pharmacokinetics*
D000143:Acids; D002257:Carbonic Anhydrase Inhibitors; D007093:Imidazoles; D054328:Proton Pump Inhibitors; D011522:Protons; C035235:Sch 28080; D010042:Ouabain; D017506:H(+)-K(+)-Exchanging ATPase; D012413:Rubidium