Casein phosphopeptides enhance paracellular calcium absorption but do not alter temporal blood pressure in normotensive rats

Abstract

Casein phosphopeptides (CPP) were purified from an in vitro tryptic digestion of casein and used for in vitro calcium binding affinity experiments to determine the optimal binding characteristics of CPP. These studies were followed by animal feeding trials designed to examine the absorption of 45Ca from the distal part of the small intestine. Male Wistar rats were meal-fed isonitrogenous diets containing casein, whey protein, soy protein isolate (SPI) or a milk protein concentrate (MPC) with adequate dietary calcium (0.7%) for a 10-week period. The absorption of 45Ca was measured from the disappearance of 45Ca from a ligated ileum loop. There were no differences in body weight gain or plasma Ca, Mg, K, Na and Ca +2 between animal groups fed the different protein sources. The 45Ca absorption from the ileum was significantly (P<0.05) lower in SPI than casein or MPC fed rats. Similarly, the apparent absorption of 40Ca was also significantly (P<0.05) higher in casein and MPC fed animals than both the SPI and whey protein-fed counterparts. These results were supported by a relatively higher amount of organic phosphorus recovered from ligated ileal loops of both casein and MPC fed animals. Despite the apparent enhancement in paracellular calcium absorption in casein and MPC groups, no differences in either systolic or mean blood pressures of rats fed the selected dietary proteins were observed.