Effect of low phosphorus diets on intestinal calcium absorption and the concentration of calcium-binding protein in intact and parathyroidectomized pigs.

The effect of changing the dietary concentration of phosphorus on the intestinal absorption of calcium has been studied in conscious pigs each prepared with a Thiry--Vella loop of jejunum. A reduction in the percentage of phosphorus in the diet from 0.7 to 0.3% caused an increase in the efficiency of absorption of calcium from the fluid used to perfuse the jejunal loop in both intact and parathyroidectomized animals. There was a marked increase in the amount of calcium-binding protein (CaBP) in the small intestine of pigs fed the low phosphrous diet. Parathyroidectomy did not affect the amount of CaBP in the small intestine when either the normal or the low phosphorus diets were fed.