Influence of sodium and parathyroid hormone on calcium release from intestinal mucosal cells

The uptake and release of (45)Ca from the intestinal mucosal epithelium were investigated under a variety of conditions. The initial rate of uptake characterized a calcium pool with a half-time of saturation of less than 2 min. The entry of (45)Ca into this pool was inhibited by NaCN and ethacrynic acid and was stimulated by the removal of Cl(-) from the incubation. The initial rate of (45)Ca release was also inhibited by NaCN and removal of Na(+) from the incubation. Parathyroid hormone administration enhanced the release of (45)Ca from cells prepared from parathyroid-ectomized animals. These observations suggest that calcium transport across the brush border and basallateral membranes are identifiable components of the kinetics of (45)Ca uptake and release and that parathyroid hormone stimulates a sodium-dependent mechanism of calcium transport across the basal-lateral membranes.