title: Suppression of ouabain-insensitive K-ATPase activity in rabbit nephron segments during chronic hyperkalemia.
abstract: Recently, we demonstrated that an ATPase stimulated by K (and not inhibited by ouabain, Na-K-ATPase inhibitor) is present in the connecting tubule (CNT) and collecting duct segments of the rabbit. In this study, we determined the effects of high- and low-K diet on K-ATPase activity in the CNT and collecting duct segments of rabbit. One group of animals was given a low-K diet (34 mEq/kg diet) and the other group was given a high-K diet (700 mEq/kg diet) for 1 week. K-ATPase activity was measured by a microfluorometric assay in which ATP hydrolysis is coupled to oxidation of NADH. Low-K animals had plasma K = 3.1 +/- 0.2 as compared with 5.5 +/- 0.5 mEq/l in high-K animals. Low-K animals had significant K-ATPase activity in CNT, CCD (cortical collecting duct) and MCD (medullary collecting duct). On the other hand, K-ATPase activity in all 3 segments from high-K animals was not significantly different from zero. These results support a hypothesis that chronic K loading suppresses the ouabain-insensitive K-ATPase in the distal nephron.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville.
authors.forename: L C
authors.initials: LC
authors.lastname: Garg
authors.forename: N
authors.initials: N
authors.lastname: Narang
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D027682:Cation Transport Proteins; D002908:Chronic Disease; D004032:Diet; D006947:Hyperkalemia / Q000201:enzymology*; D007684:Kidney Tubules / Q000201:enzymology*; D007685:Kidney Tubules, Collecting / Q000201:enzymology; D007686:Kidney Tubules, Distal / Q000201:enzymology; D008297:Male; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000097:blood / Q000494:pharmacology / Q000652:urine; D011817:Rabbits; D012964:Sodium / Q000097:blood / Q000652:urine; D000254:Sodium-Potassium-Exchanging ATPase; D014638:Vanadates / Q000494:pharmacology
chemical_list: D027682:Cation Transport Proteins; D014638:Vanadates; D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; C022761:potassium transporting ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium