Follicle and extrafollicular tissue interaction in 17 alpha,20 beta-dihydroxy-4-pregnen-3-one-stimulated ovulation and prostaglandin synthesis in the yellow perch (Perca flavescens) ovary

Intact (attached to extrafollicular (EF) tissue) yellow perch follicles ovulate in vitro when stimulated with the steroid, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20-PG). However, follicles isolated from EF tissue will not ovulate under 17,20-PG stimulation. In the present study, the interaction of follicles and EF tissue in 17,20-PG-stimulated ovulation and prostaglandin synthesis was investigated by separating follicles from EF tissue at specific times during incubation. Following separation, the incubation of isolated follicles and EF tissue was continued. At 48 hr of incubation, isolated follicles were assayed for ovulation and the media of isolated follicle and EF tissue incubates were assayed by RIA for prostaglandin E (PGE) and prostaglandin F (PGF) levels. Steroid-stimulated follicles, isolated from EF tissue prior to 22 hr of incubation, ovulated less than 25%. However, there was a very large increase in the percentage ovulation in follicles separated from EF tissue from 24 to 32 hr. PGF levels increased significantly in 17,20-PG-stimulated follicles isolated from EF tissue after 22 hr. In contrast, mean PGE levels in steroid-stimulated follicle incubates appeared to be lower than control levels. Compared with controls, PGE and PGF levels were significantly lower in incubates of isolated EF tissue stimulated with 17,20-PG, and this did not appear to be related to the time of separation. The results demonstrate that follicles must interact with EF tissue for a specific length of time for ovulation and PGI: synthesis to occur in isolated follicles. Further, the effects of 17,20-PG on prostaglandin synthesis appear to be specific for different tissue compartments. (C) 1997 Academic Press