Deoxyribonucleic acid polymerase-alpha activity in hamster follicles during the estrous cycle: roles of follicle stimulating hormone and luteinizing hormone.

In the hamster, DNA polymerase-alpha (Pol-alpha) in follicles at stages 1-4 (1-4 layers granulosa cells and no theca) increased significantly during the proestrous (P) gonadotropin surges, remained high on estrus (E) and then declined to low levels by 09.00 h, proestrus (P). However, Pol-alpha in stages 5-8 (large preantral to small antral stages) remained steady throughout the cycle. Hypophysectomy on metestrus decreased Pol-alpha by 17 h which was reversed by 2.5 micrograms follicle stimulating hormone (FSH) but not by luteinizing hormone (LH) (2.5 micrograms) or human chorionic gonadotropin (hCG) (1 IU). Hypophysectomy on E resulted 72 h later in a fall in Pol-alpha in stages 1-6; FSH (2.5 micrograms) or LH (2 micrograms) restored enzyme activity within 5 h to stages 1-6 and 5-6, respectively. Thus, Pol-alpha in the smallest preantral follicles is induced by FSH; however, for large preantral and antral follicles, steady levels are maintained by tonic FSH and LH resulting in no apparent change in enzyme activity during active DNA synthesis.