Regulation of Na+-Pi cotransport by 1,25-dihydroxyvitamin D3 in rabbit duodenal brush-border membrane.
Brush-border membrane vesicles were isolated from rabbit duodenum by a Mg2+ precipitation method, and phosphate transport was analyzed by a rapid filtration technique. Uptake of inorganic phosphate (Pi) was stimulated by an inwardly directed sodium gradient, indicating the operation of a Na-Pi cotransport system in brush-border membrane vesicles. Treatment of the animals with ethane-1-hydroxy-1,1-diphosphonate (EHDP), which is known to decrease the circulating levels of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], reduced within 3 days the sodium-dependent Pi transport in the brush-border vesicles. Injections of 1,25(OH)2D3 into rabbits increased within 9 h the sodium-dependent Pi transport in membranes from EHDP-treated animals as well as in untreated ones. The Na-D-glucose cotransport system appeared to be unaffected by these maneuvers. These results suggest that the Na-Pi cotransport system is an important site of regulation of intestinal transepithelial Pi transport by 1,25(OH)2)D3.
D000818:Animals; D001692:Biological Transport; D002117:Calcitriol / Q000502:physiology*; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism*; D005591:Chemical Fractionation; D004386:Duodenum / Q000648:ultrastructure*; D008297:Male; D008871:Microvilli / Q000378:metabolism*; D009994:Osmolar Concentration; D010710:Phosphates / Q000378:metabolism*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism* / Q000502:physiology
D010710:Phosphates; D012964:Sodium; D002117:Calcitriol