Effects of semistarvation on large intestinal calcium transport: in vivo studies in the rat

Abstract

In the semistarved rat, body, and gut growth are impaired, metabolism of vitamin D is thought to be abnormal and in vitro duodenal calcium transport is depressed. Since large intestinal calcium transport may have a role in calcium homeostasis, we studied calcium transport by cecum and colon in young semistarved rats. Animals were fed ad libitum (control group) or restricted to 50% of ad libitum food intake (semistarved group). After 11 to 14 days, calcium transport was studied in situ by intraluminal perfusion of cecum and colon with 1.2 mm calcium in saline with tracer 45Ca to determine net calcium movements and lumen-to-plasma flux. Calcium transport by the entire segment (total transport) and per gram dry weight of segment (specific transport) was measured. Specific net absorption and lumen-to-plasma flux of calcium by cecum was nearly twice as great in semistarved animals as in controls, but there was no difference between groups in colon. Cecal and colonic gut mass was decreased in semistarved animals as compared with controls. Despite gut atrophy, total transport per segment did not change with semistarvation in cecum, because of increased specific transport. In colon, semistarvation decreased total lumen-to-plasma flux, but there was no significant effect on total net movements, presumably due to depressed plasma-to-lumen flux. These findings suggest that, in the rat, the large intestine may contribute to maintaining calcium homeostasis in semistarvation.