(Ca2+ + Mg2+)-ATPase activity in plasma membrane of circulating mononuclear cells: Lack of a direct effect of vitamin D

S. Morimoto, S. J. Birge, V. Shen, L. V. Avioli

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Abstract

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 < 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 < 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.

Original languageEnglish
Pages (from-to)14953-14957
Number of pages5
JournalJournal of Biological Chemistry
Volume260
Issue number28
StatePublished - Jan 1 1985

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