Zinc status and serum levels of retinol-binding protein, tocopherol and lower density lipoproteins in male and female rats fed on semi-purified diets containing rapeseed protein or casein.

Abstract

Experiments were carried out in order to evaluate the effect of various levels of dietary zinc supplementation on the zinc status, growth and contents of retinol-binding protein (RBP), tocopherol and lower density lipoproteins (VLDL + LDL) in serum of rats fed on diets containing rapeseed protein concentrate (RPC) or casein as the sole source of protein. In male rats fed on RPC diet at a 10% protein 5% fat level, a highly significant correlation was found between dietary zinc content and the total tibia zinc content (r = 0.946) in the dietary zinc range of 35-137 microgram/mg. In contrast, the casein rats attained almost maximal bone zinc contents even at the lower level of dietary zinc. No correlation was found between zinc status and the protein efficiency ratio obtained for the rapeseed protein. In female rats fed on a zinc-supplemented RPC diet at a 20% protein and 10% fat level, the serum levels of tocopherol and VLDL + LDL were reduced in comparison to the levels observed in female rats fed on a corresponding casein diet. No diet-related changes in serum levels of RBP were found. However, male rats showed significantly higher RBP values than the female rats.