Effect of vitamin D on transepithelial phosphate transport in chick intestine

The transport of phosphate (Pi) by everted gut sacs prepared from chick small intestine has been Iinvestigated. Vitamin D increased the concentration ratio of Pi across all intestinal segments, with the greatest re:;ponse occurring in the je-junum. In this segment, Pi uptake was by a saturable process, with a V,,, of 0.32 and 0.13 pmol/g tissue per min and a K, of 0.19 and 0.20 mM in the presence or absence of vitamin D, respectively. Only the V,,, was significantly affected by vitamin D. The transport of Pi was not dependent on the presence of calcium in the mucosal solution, and absorbed Pi does not appear to enter the total mucosal pool of Pi. Influx tinal phosphate transport system in the chick and the influence of vitamin D on it. Repletion of the rachitic animals with vitamin D3 stimulated Pi translocation primarily in the jejunum and the ileum. In the ileum