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Abstract

Publisher Summary: This chapter discusses the problem of plasma membrane-bound Mg-adenosine triphosphatase (ATPase) in rat kidney and experimentally proves the existence of an anion-sensitive Mg²⁺- ATPase in brush border membranes from rat kidney cortex. It is possible to differentiate between this enzyme and a mitochondrial Mg-ATPase from the same tissue using substances such as atractyloside and filipin that interact exclusively with mitochondria or brush border membranes. Parallel studies on Mg-ATPase activity of mitochondrial and brush border fractions reveal that the enzyme in both fractions is stimulated by oxyanions—such as sulfite and bicarbonate—and is inhibited by aurovertin and oligomycin. The mitochondrial ATPase activity shows a higher sensitivity to the stimulators and inhibitors with a difference in the response of Mg-ATPase activity of the two fractions that has been obtained using atractyloside—an inhibitor of the mitochondrial adenine nucleotide translocator—and filipin—an antibiotic interacting with cholesterol in the brush border membrane. The use of filipin might provide a tool to further investigate the relationship between brush border Mg-ATPase and protein translocation in vitro and in vivo.