(Ca2+ + Mg2+)-ATPase activity in plasma membrane of circulating mononuclear cells. Lack of a direct effect of vitamin D.
The in vivo effect of vitamin D on (Ca2+ + Mg2+)-ATPase activity was examined in a plasma membrane fraction of rat circulating mononuclear cells (MPM). Although there was no significant difference in the ATPase activities in red blood cell ghosts, (Ca2+ + Mg2+)-ATPase activity in MPM was significantly higher (p less than 0.05) in long-term vitamin D3-replete rats (100 IU/day for 6 months) than that in vitamin D-deplete rats (for 6 months). In rats maintained on vitamin D-deficient diets for 5-7 weeks, in vivo administration of either vitamin D3, 2,000 IU orally, 5 days prior to killing or 1,25-dihydroxyvitamin D3, 2.4 nmol, intraperitoneally, 24 h prior to killing failed to show any significant effect on (Ca2+ + Mg2+)-ATPase activity in MPM. (Ca2+ + Mg2+)-ATPase activity in MPM from rats maintained on vitamin D-deficient diet with high calcium content (1.8%) was significantly higher (p less than 0.05) than that from rats maintained on vitamin D-deficient diet with low calcium content (0.3%). Moreover, in vitro addition of vitamin D3 metabolites did not show any effect on (Ca2+ + Mg2+)-ATPase activity in MPM. These data suggest that decreased (Ca2+ + Mg2+)-ATPase activity in MPM from long-term vitamin D-deplete rats resulted from an adaptation to low extracellular calcium rather than vitamin D depletion.
Morimoto
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Birge
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Shen
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Avioli
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D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000097:blood*; D002117:Calcitriol / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000097:blood*; D002462:Cell Membrane / Q000201:enzymology; D004910:Erythrocyte Membrane / Q000201:enzymology; D008297:Male; D009000:Monocytes / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014807:Vitamin D / Q000494:pharmacology*
D014807:Vitamin D; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002117:Calcitriol; D002118:Calcium