Effects of the type of dietary fat at two levels of vitamin E in Wistar male rats during development and aging. I. Life span, serum biochemical parameters and pathological changes.

This experiment was designed to study in rats the implications of the dietary type of fat at two levels of vitamin E on the life span as well as on several biochemical and anatomopathological age-related changes. For this purpose, six different isoenergetic diets containing 15% coconut oil (SFD), safflower oil (UFD) or a combination of both (CFD) with 2 or 200 mg% of dl-alpha-tocopherol were offered ad libitum to outbred Wistar male rats from weaning to senescence. The results indicated that up to 9--12 months the body weights of rats consuming the CFD or the UFD increased generally faster than those fed the SFD, and that all rats developed moderate degrees of obesity. Age-dependent changes in organ weights (kidneys, testes, spleen, brain, liver and heart) were unaffected by diet. Serum levels of vitamin E generally reflected the corresponding dietary levels, but were also influenced by the type of dietary fat. Serum cholesterol levels were not significantly affected by the type of diet or by age. Only transient hypotriglyceridemic and hypophospholipidemic effects of the UFD were observed and, while the levels of triglycerides decreased with age up to the 18th month followed by an increase at 24 months, the levels of serum phospholipids remained unchanged. Neither diet nor age modified the serum albumin/globulin ratios. While no differences in maximum life span were found between dietary groups, the 50% survival time of rats fed the UFD at high level of vitamin E was significantly longer than in all the other groups. This beneficial effect was related to postponement of the onset and reduction of incidence of malignant neoplasms, but was apparently not related to any particular influence on the incidence or severity of chronic nephropathy which practically developed in all rats. Various neoplastic, degenerative and inflammatory diseases encountered in rats dying during the course of the experiment were tabulated and compared with similar findings reported by others in different strains of rats. Pituitary and adrenocortical adenomas as well as adrenocortical and renal carcinomas were the most frequent tumors found in this study. All the pathological changes provided useful baseline information for the evaluation of data presented in this and subsequent communications of this series of studies.