EFFECT OF AN INORGANIC AND ORGANIC FORM OF DIETARY SELENIUM ON THE PROMOTIONAL STAGE OF MAMMARY CARCINOGENESIS IN THE RAT

  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (7) , 2803-2806
Abstract
The relative effectiveness of either sodium selenite or selenomethionine in the inhibition of mammary carcinogenesis was studied in virgin female Sprague-Dawley rats. In 1 experiment, rats were given 50 mg of 1-methyl-1-nitrosourea per kg of body wt s.c. at 50 days of age. Beginning 7 days post-1-methyl-1-nitrosourea, they were assigned to a basal diet containing 0.1 ppm of Se or basal diet supplemented to contain either 4, 5 or 6 ppm of Se as sodium selenite or 5 or 6 ppm of Se as selenomethionine. Selenium treatment was continued until termination of the study 135 days after 1-methyl-1-nitrosourea treatment. Sodium selenite at the 5 ppm level was the most effective chemopreventive agent. The highest level of selenomethionine (6 ppm) caused grossly apparent liver damage. No liver damage was noted in sodium selenite-treated rats. In a 2nd experiment, rats were given 5 mg of 7,12-dimethyl-benz(a)anthracene at 50 days of age. Beginning 7 days after 7,12-dimethylbenz(a)anthracene treatment, rats were assigned randomly to the control group or to 1 of 2 Se treatment groups receiving either 3.4 ppm of Se as sodium selenite or 3.4 ppm as selenomethionine in their drinking water. Se supplementation was continued throughout the study until its termination at 111 days postcarcinogen. Sodium selenite significantly reduced cancer incidence and the average number of cancers per rat. Treatment with selenomethionine was less effective and caused severe liver damage. Although both sodium selenite and selenomethionine can inhibit some aspect of the postinitiation stage(s) of mammary carcinogenesis, Se provided as sodium selenite was the more effective and less toxic of the 2 chemicals. Increasing the dose of sodium selenite above 5 ppm did not enhance the inhibitory activity of Se.