MICROPHOTOMETRIC STUDY OF Δ5-3β-HYDROXYSTEROID DEHYDROGENASE IN THE OVARIES OF RATS FED ON HIGH FAT DIETS IN RELATION TO 7, 12-DIMETHYLBENZ (A)-ANTHRACENE MAMMARY TUMORS
1984 年 17 巻 5 号 p. 533-545
詳細
1984 年 17 巻 5 号 p. 533-545
Female Wistar-Imamichi rats, were given 7, 12-dimethylbenz(a)anthracene (DMBA), and then three different high fat (HF) diets containing olive, safflower, and corn oil, respectively, for 120 days. Mammary tumors developed in O of 10 rats fed on a corn oil diet (C), 2 of 10 rats fed on an olive oil diet (O), and 2 of 10 rats fed on a safflower oil diet (S). In the tumor-bearing rats fed on O and S diets with DMBA treatment, the levels of the plasma progesterone were higher than those of control rats on the same diets without DMBA treatment. The levels of plasma progesterone of the tumor bearing rats fed on C diet were no difference compared with that of control.
The plasma 17β-estradiol levels in tumor-bearing rats on different diets were similar.
Changes of 3β-hydroxysteroid dehydrogenase (3β-HSD; EC 1.1.1.51) activity in the ovaries of mammary tumor bearing rats fed on HF diets were examined by the microspectrophotometric method. In mammary tumor-bearing rats of HF diets, the activity was higher than that of control rats in the corpus luteum and interstitial gland in the ovaries, but not in the thecal membrane. The activity tended to increase with diet in the order C, S, and O. In particularly, in the ovaries of the tumor-bearing rats fed on O, the secondary corpus luteum (CL 2) and the primary corpus luteum (CL 1) showed high activity. These showed that high content of oleic acid contained in olive oil may induce an increase of progesterone production in their ovaries. In control rats, the activity in CL 2 in the ovaries was lower than that in CL 1.
These results suggest that the increases in plasma progesterone in tumor-bearing rats on O or S may have been caused by prolonged corporus luteum function and the active formation of interstitial glands in the ovaries. This resulted in a low incidence of mammary tumors because continuous stimulation of progesterone caused lobulo-alveolar proliferation, thereby protecting the mammary epithelium from carcinogens.
