title: 1,25-Dihydroxyvitamin C3-stimulated active uptake of phosphate by rat jejunum.
abstract: An assay system for measuring an active phosphate uptake in rat jejunal disks has been developed and used to study the rat's response to 1,25-dihydroxyvitamin D3. The active component of phosphate uptake is stimulated by added KCl, fructose, sodium, and CaCl2, but not MgCl2. Half-saturation values obtained with this assay are 0.08 mM (1,25-dihydroxyvitamin D3-treated) and 0.11 mM (D-deficient). The maximal velocities are 9.6 nmol . cm-2 . min-1 (D-deficient). Using a 5-min preincubation and a 15-min incubation, a dose-response curve for 1,25-dihydroxyvitamin D3 shows 6 pmol to be the lowest dose to give a significant response and 60 pmol to be the level at which the maximal response is reached. Measurement of phosphate uptake versus time after dosing with 1,25-dihydroxyvitamin D3 (300 pmol) revealed a biphasic response with peaks at 8 and 36 h and a trough at 20 h.
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D002122:Calcium Chloride / Q000494:pharmacology; D005632:Fructose / Q000494:pharmacology; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010101:Oxygen Consumption; D010710:Phosphates / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats
chemical_list: D010710:Phosphates; D005632:Fructose; D011189:Potassium Chloride; D002117:Calcitriol; D002122:Calcium Chloride