Early effects of vitamin D metabolites on phosphate fluxes in isolated rat enterocytes.
The present studies were designed to explore the possibility that, in addition to its well-known steroidlike action, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the active vitamin D3 metabolite, modulates inorganic phosphate (Pi) transport across the intestinal mucosa through more rapid membrane effects. Enterocytes were mechanically isolated from the duodenojejunum of vitamin D-replete rats. In this model enterocyte Pi uptake was a temperature-dependent as well as a Na+-dependent process. In vitro addition of 1,25(OH)2D3 (1 pM) led to a significant increase in Na+-dependent initial Pi uptake velocity (iVpi) within 20 min (P less than 0.001). No effect was seen for shorter incubation times (5 and 15 min). Incubation of the cells with cycloheximide did not inhibit the hormone-mediated increase of iVpi. 25-Hydroxyvitamin D3 significantly increased iVPi (P less than 0.05) at a concentration of 1 nM but not 1 pM. Vitamin D3 at a concentration of 1 microM had no effect on iVPi. Enterocyte Pi efflux rate constant was not modified by the presence of 1,25(OH)2D3(1pM). Thus, the early in vitro effect of 1,25(OH)2D3 on Pi uptake by isolated enterocytes suggests a nongenomic action of the hormone, possibly by modifying the lipid structure of the plasma membrane.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D002470:Cell Survival; D000431:Ethanol / Q000494:pharmacology; D066298:In Vitro Techniques; D007583:Jejunum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008854:Microscopy, Electron; D010710:Phosphates / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D010710:Phosphates; D000431:Ethanol; D002117:Calcitriol