Effects of gastrin and secretin on intestinal calcium absorption in the rat.

We studied the effect of physiological and supraphysiological plasma levels of gastrin and secretin on duodenal calcium absorption (CaA) in the growing rat. During infusion of either synthetic human gastrin 17 I (0.05, 0.1 or 0.25 micrograms/kg BW h, i.v.), synthetic porcine secretion (0.06, 0.125 or 0.25 CU/kg BW h, i.v.) in vehicle (0.15% BSA in saline), or vehicle alone, duodenal lumen-to-plasma flux, plasma-to-lumen flux and the net absorption of calcium were determined by in situ perfusion. While plasma gastrin- or secretin-like immunoreactivity rose to postprandial-like levels with increasing infusion doses, the bidirectional Ca fluxes, serum Ca, parathyroid hormone and concomitant urinary Ca excretion were not changed by any hormone infusion as compared with rats receiving intravenous vehicle only. We conclude that a physiological short-term regulating role of these hormones in duodenal CaA is unlikely in the growing rat.