Dietary effects of menhaden oil on the growth and membrane lipid composition of rat mammary tumors.

The objective of this study was to evaluate the effect of quantitative differences in dietary menhaden oil, an n-3 polyunsaturated marine oil, on mammary tumor development and to compare these results with those produced by corn oil, an n-6 polyunsaturated vegetable oil. Inbred female BUF rats were treated with the carcinogen N-methyl-N-nitrosourea (CAS: 684-93-5) and maintained on diets containing graded levels of each of the respective oils. Our results indicated that diets containing 20% menhaden oil produced a reduction in tumor incidence and a prolongation of the tumor latent period. This finding contrasted sharply with the enhanced tumor development and shortened latent period observed in the animals fed the equivalent dietary level of corn oil. Fatty acid analyses performed on the lipids extracted from the tumor and hepatic microsomes of the animals on the menhaden oil diets demonstrated that the proportion of eicosapentaenoic acid (No. of C-atoms:No. of double bonds = 20:5) present in these microsomal lipids was related inversely to mammary tumor development.

Dietary lipid effects on the growth, membrane composition, and prolactin-binding capacity of rat mammary tumors.

The effects of qualitative and quantitative differences in dietary lipid on the growth of N-methyl-N-nitrosourea (CAS: 684-93-5)-initiated mammary tumors were evaluated in inbred female (F344) rats. Specific prolactin-binding measurements and qualitative lipid analyses were performed on both tumor and hepatic microsomes from these animals. Our results indicated that 1) when the polyunsaturated lipid component (corn oil) of the diet exceeded 3%, it was the quantitative level of total lipid, rather than the level of polyunsaturated lipid alone, that best correlated with the observed reduction in tumor latent period; 2) when the polyunsaturated lipid content of the diet fell below 3%, there was a decrease in tumor incidence and an increase in the mean latent period; 3) only those changes in tumor development that occurred when the dietary polyunsaturated lipid content was below 3% were associated with alterations in specific prolactin binding capacity.