Enhanced absorption of calcium by casein phosphopeptides in rachitic and normal chicks

The present studies were undertaken to investigate the effect of casein phosphopeptides on calcium absorption in normal and rachitic chicks. Phosphopeptides were produced by tryptic hydrolysis of casein and the crude peptide mixture was further purified, using gel filtration. The chromatographic fractions were pooled according to their protein and phosphorus content. Some of these fractions, when introduced into the ligated duodenal loop at a concentration of 1 mg/ml or added to the mucosal solution in vitro at a concentration of 0.1 mg/ml, were capable of increasing the intestinal transport of radiocalcium. This effect was seen both in the normal and rachitic chicks, indicating that the stimulatory response was not dependent upon molecular changes induced by vitamin D. Furthermore, this response was not shared by peptides from albumin, not likely due to phosphate generated from the phosphopeptides, nor related to the phosphate content of the fractions. These experiments demonstrate that a component of milk, in addition to lactose, might account for the high availability of calcium in milk.