The effects of diet supplemented with
perilla oil, which contains a large amount of n-3
alpha-linolenic acid, and n-6
linoleic acid rich soybean and
safflower oil supplemented diets on 7,12-dimethylbenz[a]
anthracene (DMBA)- and
1,2-dimethylhydrazine (
DMH)-induced mammary gland and colon
carcinogenesis were investigated in female SD rats. Groups of 23 or 24, 5 week old animals were first given three s.c.
injections of 40 mg/kg body wt
DMH followed by a single intragastric administration of 50 mg/kg body wt DMBA within 2 weeks of the commencement. Starting 1 week after the DMBA treatment, they were administered pellet diet containing 10%
perilla oil,
soybean oil or
safflower oil for the succeeding 33 weeks. Histological examination revealed that the resultant numbers of mammary
tumors per rat were significantly lower in rats given
perilla oil diet (4.4 +/- 2.5) than in the
soybean oil diet group (6.5 +/- 3.9). Furthermore, colon
tumor incidence was significantly lower in animals receiving the
perilla oil supplement (18.2%) than in those given
safflower oil diet (47.4%), and the numbers of colon
tumors per rat tended to be lowest in rats administered
perilla oil. Also the incidence of
nephroblastomas in rats receiving
perilla oil diet (0%) was significantly lower than that for the
soybean oil diet group (23.8%). The results thus indicate that the
alpha-linolenic acid (n-3)-rich
perilla oil diet inhibits development of mammary gland, colon and kidney
tumors as compared to
linoleic acid (n-6)-rich safflower or
soybean oil diet.