SIMPLE OR REPEATED INDUCTION OF SUPEROVULATION - A STUDY ON OVULATIONRATES AND MICROVESSEL CORROSION CASTS IN OVARIES OF GOLDEN-HAMSTERS

Repeatedly stimulated ovaries are reported to decrease the ovulation r ate. One cause among others might be that the microvascular bed has be en insufficiently developed. Therefore, 30-day-old golden hamsters wer e superovulated either once or repeatedly. At the light microscopic le vel, the ovulation rate in serially sectioned ovaries was indirectly d etermined by the occurrence of corpora lutea and of abnormal follicle rupture with oocyte release into the cortical stroma (IOR). For the st udy with scanning electron microscopy (SEM), the microvascular bed of the ovaries was cast with a polyester resin, and the corrosion casts o f mature follicles observed. The histological sections of once-stimula ted ovaries showed a large number of corpora lutea and IOR follicles. This indicated hyperovulation. In corrosion casts of once-stimulated o varies, large-sited antral follicles with two layers of a dense capill ary meshwork were observed. Capillary sprouts were aligned around the antrum 0 to 12 h after administration of human chorionic gonadotrophin (hCG), and these radiated towards the center of the antrum after 12 t o 36 h had elapsed. The ovulation site was recognized at the follicle apex by three similarly sized structures which were either a sinusoid, an oocyte replica, or an opening. Repeatedly stimulated ovaries produ ced a low number of corpora lutea and almost no IOR follicles. This wa s judged as hypoovulation. The microvessels of mature follicles were r educed in number and incompletely cast. Widespread resin leakages were conspicuous in the follicle wall 36 h after hCG injection, but the ca pillary sprouts radiated towards the center of the antrum. No ovulatio n site was detectable. It is concluded, that capillary sprouts are ind uced before luteinization. The ovulation site is indicated by particul ar changes in its microvascular bed. An insufficiently developed micro vascular bed may be responsible for hypoovulation in repeatedly stimul ated ovaries.