[An ultrastructural study of capillary permeability of rabbit ovarian follicles during ovulation using carbon tracer (author's transl)].

The observations that perifollicular capillaries of the ovary become engorged with prominent edema in the theca interna and externa around the time of ovulation, suggest a preovulatory increase in permeability of perifollicular capillaries. In previous study, we reported ultrastructural evidences which suggested the increased permeability of perifollicular capillaries just prior to ovulation. In this study, we further examined the perifollicular capillaries of rabbit ovary by using carbon particles as a tracer at various time intervals after the hCG injection for induction of ovulation. Pinocytotic vesicles exhibited no significant changes in size, number and distribution through all preovulatory stages. Carbon particles were not taken into them. Fenestrations were observed at 0,3,4,6 hrs after the hCG injection, most frequently at 4 hrs, but no carbon particles could penetrate them. Intercellular gaps between two adjacent endothelial cells began to be observed at 10 hrs after the hCG injection. Carbon particles passed through these gaps with staying inside the basement membrane (so-called intramural leaking). These observations indicated that the increased permeability of the perifollicular capillaries, just before ovulation, were due to intercellular gaps.