Influence of dietary fat on spontaneous lesions of Syrian golden hamsters.

Dietary corn oil was consumed by Syrian golden hamsters at levels of 4.5 g [low fat (LF)] or 18 g [high fat (HF)]/385 kilocalories (kcal) from 3 to 7 weeks of age followed by a diet containing 9 g [medium fat (MF)]/385 kcal for life. In other groups MF diet was given from 3 to 7 weeks of age and followed by either LF or HF for life. A separate group was fed MF continuously after 3 weeks of age. Spontaneous lesions, which were altered by these dietary protocols, are reported. An HF diet fed after 8 weeks increased the incidence of flank organ hyperplasia and prostatitis, but it decreased prostatic fibrosis in males. Consumption of HF diets after 8 weeks by females increased survival and resulted in an elevated incidence of thyroid adenomas, ovarian cell hyperplasia, vaginal papillomas, and adrenal cortical cell adenomas. In age-adjusted data the increase in ovarian cell hyperplasia and adrenal cortical cell adenomas was shown to be due to HF diet and not to be a consequence of extended survival. Periodontitis and calcification of cardiac tissues decreased in hamsters fed HF diets after 8 weeks, but cell vacuolization and hyperplasia of the anterior pituitary gland and epithelial hyperplasia in the forestomach were increased. Salivary gland adenocarcinomas were observed only in hamsters fed HF diets. Feeding HF levels, either during weeks 3-7 or after week 8, decreased osteofibrosis and otitis media and increased urinary bladder epithelial hyperplasia, adrenal cortical cell lipomatosis, and bone chondrosis. Calcification of gastric and renal arteries decreased as dietary fat levels increased either before or after 8 weeks of age in males and only when fed after 8 weeks in females. Colitis and focal glandular hyperplasia of the colon mucosa were increased in both sexes by an HF diet being given before or after 8 weeks of age.