排卵における卵胞壁proteinaseの役割に関する研究

抄録

The ovulation mechanism was studied on the basis of those biochemical events occurring in the ovarian follicle wall which lead to the bursting of the top of the follicle.
Bovine follicles were divided into the following 5 groups according to their sizes : 5 (4-6) mm in diameter, 10 (8-12) mm, 15 (13-17) mm, 20 (18-22) mm and 25 (over 25) mm. Protease activity in the follicle wall was estimated by measuring trypsin activity of hydrolyzing casein. Plasmin activity was determined by the fibrin plate method. The experiments revealed that the larger the follicle was in size, the higher protease activity it showed. Mature follicles with diameters of 15-25 mm were found to have the highest protease activity in their walls. However, the activity of very large follicles whose diameters were over 25 mm was quite low. Protease activity at the follicular top was remarkably high as compared with that of the surrounding area. As the follicles grew larger, their walls became thinner, especially at the top. While follicle-stimulating hormone (FSH), pregnant mare serum (PMS), human chorionic gonadotropin (HCG), and progesterone had a tendency to enhance protease activity to a small degree, estrone specifically inhibited the activity almost completely.
When HCG was administered to mature rabbits weighing 3-3.5 kg, ovulation occurred within 10 hrs after the administration. Meanwhile, when transamine (trans-4-aminocyclohexane carboxyamide), an antiplasmin, was administered concomitantly with HCG, ovulation was completely inhibited in spite of mature follicles being present in the ovaries. Serial administration of transamine after HCG resulted in complete inhibition of ovulation for 7 hrs after the administration. However, 1.5 (the average number) of more than 10 mature follicles ovulated 8 hrs after. One hour later, the number of ovulating follicles was increased to 5. These findings indicate that protease begins to show its ovulation-promoting action only 8 hrs after HCG administration; that is, the latent period of 7 hrs is necessary for protease production.
Transamine is supposed not to have any effect on plasmin already produced, but to act specifically on the proactivator or activator necessary for the production of plasmin. On the other hand, HCG was unlikely to directly affect plasmin formation, for, the addition of HCG to the fibrin plate only slightly helped activate plasmin.
In view of an activator and/or inhibitor involved in the control mechanism for protease activity, quantitative changes of a plasmin inhibitor were studied as the ovarian follicles grew larger. The amount of the inhibitor normally decreased with the growth of the follicles, but it markedly increased in follicles with ovulation disturbances.
It may be rational to suppose that the follicle wall is digested by protease with the result of disruption of ovulation, and that ovulation disturbance results not only from deficiency of LH secretion or imbalance between FSH and LH secretions, but also from de-creased protease activity or deficiency of the enzyme in the ovarian follicle wall.