Effect of dietary protein on N-nitrosobis(2-oxopropyl)amine-induced carcinogenesis and on spontaneous diseases in Syrian golden hamsters.

For assessment of the effect of dietary protein on spontaneous diseases and on the carcinogenicity of N-nitrosobis(2-oxopropyl)amine [(BOP) CAS: 60599-38-4], Syrian golden hamsters were fed either low protein (LP; 9% casein), medium protein (MP; 18% casein), or high protein (HP; 36% casein) in a diet containing a medium fat (corn oil) level. The experimental design permitted distinguishing between the effects of protein levels on initiation and development of various lesions in hamsters, in comparison with a control group that was given MP diet for life. When fed after BOP treatment, HP diet inhibited, among induced tumors, pulmonary adenomas in males. Among spontaneous diseases, LP diet fed before 8 weeks of age enhanced colitis in both males and females, renal and adrenal gland amyloidosis in males, and gastric vascular calcinosis in males but inhibited liver abscesses and liver cysts in both males and females. When fed after 8 weeks of age, LP diet enhanced gastric and renal vascular calcification and parathyroid gland adenomas in both sexes but inhibited hepatic, renal, and adrenal gland amyloidosis in females and liver abscesses and liver cysts in both males and females. The feeding of HP diet before 8 weeks of age enhanced the development of colitis and adrenal gland lipomatosis in both males and females but inhibited the development of adrenal gland amyloidosis and adrenal cortical cell hyperplasia in males. When fed to hamsters after 8 weeks of age, HP diet increased the incidence of adrenal gland amyloidosis in females and colitis in both males and females but reduced the frequency of liver cysts in both males and females and of adrenal cortical cell hyperplasia in males. The overall data and literature review indicate that the effect of dietary protein on tumorigenesis is tissue, sex, species, and strain related.