title: Regucalcin modulates hormonal effect on (Ca(2+)-Mg2+)-ATPase activity in rat liver plasma membranes.
abstract: The interaction of various hormones and regucalcin on (Ca(2+)-Mg2+)-ATPase activity in rat liver plasma membranes was investigated. The presence of epinephrine (10(-6)-10(-4) M), phenylephrine (10(-6)-10(-4) M), and insulin (10(-8)-10(-7) M) in the reaction mixture produced a significant increase in (Ca(2+)-Mg7+)-ATPase activity, while the enzyme activity was decreased significantly by calcitonin (3 x 10(-8)-3 x 10(-6) M). These hormonal effects, except for calcitonin, were clearly inhibited by the presence of vanadate (10(-4) M) which can inhibit the Ca(2+)-dependent phosphorylation of enzyme. Meanwhile, regucalcin (0.25 and 0.50 microM), isolated from rat liver cytosol, elevated significantly (Ca(2+)-Mg2+)-ATPase activity in the plasma membranes, although this elevation was not inhibited by vanadate (10(-4) M). The epinephrine (10(-5) M) or phenylephrine (10(-4) M)-induced increase in (Ca(2+)-Mg2+)-ATPase activity was disappeared in the presence of regucalcin; in this case the effect of regucalcin was also weakened. However, the inhibitory effect of calcitonin (3 x 10(-6) M) was not weakened by the presence of regucalcin (0.5 microM). Moreover, GTP (10(-5) and 10(-4) M)-induced increase in (Ca(2+)-Mg2+)-ATPase activity was not seen in the presence of regucalcin (0.25 microM). The present finding suggests that the activating mechanism of regucalcin on (Ca(2+)-Mg2+)-ATPase is not involved on GTP-binding protein which modulates the receptor-mediated hormonal effect in rat liver plasma membranes.
authors.affiliation: Laboratory of Metabolism and Endocrinology, Graduate School of Nutritional Sciences, University of Shizuoka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000187:drug effects*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002265:Carboxylic Ester Hydrolases; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004347:Drug Interactions; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006728:Hormones / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D009243:NAD / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015238:Sulfotransferases
chemical_list: D002135:Calcium-Binding Proteins; D006728:Hormones; D047908:Intracellular Signaling Peptides and Proteins; D009243:NAD; D006160:Guanosine Triphosphate; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D017301:Ca(2+) Mg(2+)-ATPase