Intestinal maturation: effect of luminal osmolality on net mineral secretion.

We investigated with an in vivo single-pass perfusion technique net secretion of calcium, magnesium, and zinc from proximal and distal small intestinal segments and from the cecum plus colon segments of suckling, weanling, and adolescent rats during perfusion with either isotonic (300 mOsm/kg) or hypertonic (500 mOsm/kg) mineral-free solutions. There was not secretion of calcium, magnesium, and zinc in all segments perfused at all age periods. During isotonic perfusion, rates of net secretion of calcium and zinc were severalfold greater in the proximal and distal segments of the suckling rats compared with the corresponding segments of the adolescent rats.