title: Quantitative changes in ovarian 17 alpha-hydroxylase/C17,20-lyase and aromatase activities during the estrous cycle of the hamster.
abstract: Aromatase activity of the microsomal fraction of ovarian homogenates, measured by a tritium exchange assay using androstenedione (A-dione) as substrate, did not change during the 4-day estrous cycle of the hamster. In contrast, 17 alpha-hydroxylase, measured by a tritium exchange assay with progesterone as substrate, and particularly C17,20-lyase activity, evaluated by acetic acid production from progesterone, drastically decreased on the afternoon of proestrus (Day 4). The latter two activities remained low on Days 1 and 2 but increased dramatically on Day 3 and the morning of Day 4. The serum concentration of A-dione and 17-hydroxyprogesterone reached a peak at 1600 hr of proestrus and then decreased rapidly as the enzyme activities decreased. A-dione levels were undetectable on Day 1 but 17-hydroxyprogesterone levels remained elevated through Day 2. The results are consistent with the view that 17 alpha-hydroxylase and C17,20-lyase are activities of a single cytochrome P-450, as has been shown for testis and adrenal. Increases in hydroxylase and lyase activities occur concomitantly with decreases in the serum concentrations of progesterone, suggesting that the latter steroid may play a role in controlling these enzymes.
mesh_terms: D019326:17-alpha-Hydroxyprogesterone; D000446:Aldehyde-Lyases / Q000378:metabolism*; D000735:Androstenedione / Q000097:blood; D000818:Animals; D001141:Aromatase / Q000378:metabolism*; D006224:Cricetinae; D004958:Estradiol / Q000097:blood; D004971:Estrus; D005260:Female; D006908:Hydroxyprogesterones / Q000097:blood; D010053:Ovary / Q000201:enzymology*; D011359:Proestrus; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism*
chemical_list: D006908:Hydroxyprogesterones; D000735:Androstenedione; D004958:Estradiol; D019326:17-alpha-Hydroxyprogesterone; D013250:Steroid Hydroxylases; D001141:Aromatase; D013254:Steroid 17-alpha-Hydroxylase; D000446:Aldehyde-Lyases