Effect of Dietary Protein Source and Corn Oil and Cellulose Levels on Strontium-calcium Discrimination in Growing Rats

Abstract

The effect of diet composition on strontium-calcium discrimination in the growing rat was investigated using tracer doses of 89Sr and 45Ca administered by stomach tube to both sexes in a 2 × 2 × 3 factorial experiment whose variables in addition to sex (S) were protein (P), casein or zein at a 20% dietary level, cellulose (C), at a 3 or 12% dietary level, and corn oil (CO), at a zero, 4 or 8% dietary level. Criteria of response were the 2-hour disappearance of each isotope from the gastrointestinal tract, content of each isotope in the femurs and blood serum (expressed as percentage of administered dose) and the following 89Sr/45Ca ratios; that absorbed from the gastrointestinal tract, that contained in femurs and that contained in blood serum. Significant main effects of treatments were: casein produced 41 and 42% greater absorption and 48 and 59% greater femur content of 89Sr and 45Ca, respectively, than zein, but did not alter either 89Sr/45Ca absorbed or 89Sr/45Ca in femurs. Casein produced a 69% reduction of serum 45Ca as compared with zein which caused the 89Sr/45Ca in serum to be 534% greater than the value for zein. When dietary cellulose increased from 3 to 12%, 89Sr of bone and 45Ca of serum were decreased by 21 and 25%, respectively. Male rats had 34 and 14% smaller quantities of femur 89Sr and 45Ca, respectively, than females. The main effect of dietary level of CO was nonsignificant. Significant interactions for respective criteria were: absorbed 45Ca, C with CO; bone 89Sr, C with CO; bone 45Ca, C with CO; 89Sr/45Ca in femur, P with S and P with CO; serum 89Sr, P with C; and serum 45Ca, P with C and S with C.