title: The importance of the non-protein components of the diet in the plasma cholesterol response of rabbits to casein.
abstract: To characterize the hypercholesterolaemic effect of casein further, four groups of young male rabbits in two separate experiments were placed on cholesterol-free semi-purified diets for 12 weeks. The diets were similar in composition, with either casein or soya-bean-protein isolate providing the protein source (250 g/kg). In two of these diets the salt mix was reduced by 45% (normally 40 g/kg) and replaced by potassium bicarbonate. Growth was unaffected by these alterations in dietary salts except for one group given the soya-bean-reduced-salts diet. The mean concentrations of plasma cholesterol were significantly higher in all casein-fed groups as compared with their soya-bean-fed counterparts but the response was much greater in those given the casein-reduced-salts diet. Contrary to expectations, analysis of the diets showed the zinc and copper concentrations of the casein diets to be less than those of the soya-bean diets. This was due to the greater concentrations of Cu (threefold) and Zn (twofold) in the soya-bean-protein isolate compared with casein. The mean concentration of Zn in fur was significantly decreased in casein-fed rabbits and these animals also excreted less Zn but more Cu in their urine than those given the casein-reduced-salts diet. The rabbits given the casein diet with the least salt mix showed the greatest degree of hypercholesterolaemia, suggesting an interaction between trace elements and the casein effect.
mesh_terms: D000818:Animals; D001835:Body Weight; D002364:Caseins / Q000008:administration & dosage* / Q000494:pharmacology; D002784:Cholesterol / Q000097:blood*; D003300:Copper / Q000032:analysis / Q000652:urine; D004032:Diet; D006197:Hair / Q000032:analysis; D006937:Hypercholesterolemia / Q000139:chemically induced; D008099:Liver / Q000032:analysis; D008297:Male; D011817:Rabbits; D015032:Zinc / Q000032:analysis / Q000652:urine
chemical_list: D002364:Caseins; D003300:Copper; D002784:Cholesterol; D015032:Zinc