title: Characterization of ATP-dependent Ca2+ transport in the basolateral membrane vesicles from proximal and distal tubules of the rabbit kidney.
abstract: Basolateral membrane vesicles were prepared from purified proximal and distal tubules of the rabbit kidney. The properties of the ATP-dependent Ca2+ transport were investigated. In both membranes, there was a high affinity, ATP-dependent Ca2+ transport system (Km = 0.1 microM). The optimal concentration of Mg2+ was 0.5 mM and the optimal concentration of ATP was 1 mM. The nucleotide specificity and pH dependence of the Ca2+ transport in both membranes were similar. In basolateral membrane vesicles, calmodulin had no effect on Ca2+ transport. However, in basolateral membrane vesicles depleted of calmodulin, exogenous calmodulin increased the Ca2+ transport by increasing maximal velocity. There were no major differences in the properties of the ATP-dependent Ca2+ transport system in these two membranes. These findings are discussed in relation to why parathyroid hormone differentially modulates Ca2+ transport in these two segments of the nephron.
authors.affiliation: Maisonneuve-Rosemont Research Center, Montréal, Que., Canada.
authors.forename: C
authors.initials: C
authors.lastname: Ramachandran
authors.forename: M
authors.initials: M
authors.lastname: Chan
authors.forename: M G
authors.initials: MG
authors.lastname: Brunette
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002147:Calmodulin / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009711:Nucleotides / Q000494:pharmacology; D010281:Parathyroid Hormone / Q000378:metabolism; D011817:Rabbits; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D008565:Membrane Proteins; D009711:Nucleotides; D010281:Parathyroid Hormone; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D002118:Calcium