title: Further evidence for the existence of an intrinsic bicarbonate-stimulated Mg2+-ATPase in brush border membranes isolated from rat kidney cortex.
abstract: The aim of this study was to provide further evidence for the existence of a nonmitochondrial becarbonate-stimulated Mg2+-ATPase in brush border membranes derived from rat kidney cortex. A plasma membrane fraction rich in brush border microvilli and a mitochondrial fraction were isolated by differential centrifugation. Both fractions contain a Mg2+-ATPase activity which can be stimulated by bicarbonate. The two Mg2+-ATPases are stimulated likewise by chloride, bicarbonate, and sulfite or inhibited by oligomycin and aurovertin, though to different degrees. In contrast to these similarities, only the Mg2+-ATPase activity of the mitochondrial fraction is inhibited by atractyloside, a substance which blocks an adenine nucleotide translocator in the inner mitochondrial membrane. On the other hand, filipin, an antibiotic that complexes with cholesterol in the membranes inhibits exclusively the Mg2+-ATPase of the cholesterol-rich brush border membranes. Furthermore it could be demonstrated by the use of bromotetramisole, an inhibitor of alkaline phosphatase activity, that the Mg2+-ATPase activity in the membrane fraction is not due to the presence of the highly active alkaline phosphatase in these membranes. These results support the assumption that an intrinsic bicarbonate-stimulated Mg2+-ATPase is present in rat kidney brush border membranes.
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001278:Atractyloside / Q000494:pharmacology; D001313:Aurovertins / Q000494:pharmacology; D001639:Bicarbonates / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology*; D007672:Kidney Cortex / Q000201:enzymology / Q000648:ultrastructure*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008871:Microvilli / Q000201:enzymology*; D008928:Mitochondria / Q000201:enzymology; D009840:Oligomycins / Q000494:pharmacology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D001313:Aurovertins; D001639:Bicarbonates; D009840:Oligomycins; D001278:Atractyloside; D000469:Alkaline Phosphatase; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium