Experimental protein malnutrition decreases calcium-binding protein in rat intestinal mucosa.

Calcium-binding activity was measured in duodenal mucosal homogenates of rats 50 days after weaning onto a protein-deficient diet providing 3-4 g of protein per kilogram of body weight per day compared to control animals, who were fed an isocaloric diet providing 9-12 g of protein per kilogram of body weight per day. Calcium-binding activity was decreased (44% of control) further than can be explained by the decrease in intestinal mucosal weight (70% of control) or supernatant protein content (80% of control). The results suggest that the decrease in calcium-binding activity reflects decreased synthesis of the vitamin D-dependent calcium-binding protein (CaBP) as an adaptive response to the stunted growth associated with protein malnutrition.