title: Regucalcin increases Ca2+-ATPase activity and ATP-dependent calcium uptake in the microsomes of rat kidney cortex.
abstract: The effect of regucalcin, a Ca2+-binding protein, on Ca2+ transport system in rat renal cortex microsomes was investigated. The presence of regucalcin (10[-8] to 10[-6] M) in the reaction mixture caused a significant increase in Ca2+-ATPase activity and ATP-dependent 45Ca2+ uptake in the microsomes. Regucalcin (10[-7] M) increased Ca2+-ATPase activity independently of increasing concentrations of CaCl2. The microsomal Ca2+-ATPase activity and 45Ca2+ uptake were markedly decreased by the presence of vanadate (0.1 mM) or N-ethylmaleimide (NEM; 5 mM) in the absence or presence of regucalcin. Dithiothreitol (DTT; 5 mM) markedly elevated Ca2+-ATPase activity and 45Ca2+ uptake in the microsomes. The DTT effects were not further enhanced by regucalcin (10[-7] M). Meanwhile, the microsomal Ca2+-ATPase activity and 45Ca2+ uptake were significantly decreased by the presence of dibutyryl cyclic AMP (DcAMP; 10[-5] and 10[-3] M) or inositol 1,4, 5-trisphosphate (IP3; 10[-7] and 10[-5] M). The effect of regucalcin (10[-7] M) on Ca2+ATPase activity and 45Ca2+ uptake was weakened in the presence of DcAMP or IP3. The present results demonstrate that regucalcin has a stimulatory effect on ATP-dependent Ca2+ uptake in the microsomes of rat renal cortex due to acting on the thiol groups of Ca2+-ATPase.
authors.affiliation: Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka City, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kurota
authors.forename: M
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases; D004789:Enzyme Activation / Q000187:drug effects; D047908:Intracellular Signaling Peptides and Proteins; D007672:Kidney Cortex / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015238:Sulfotransferases
chemical_list: D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D000255:Adenosine Triphosphate; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D000252:Calcium-Transporting ATPases; D002118:Calcium