PROSTAGLANDINS AND SEX STEROIDS FROM REPTILIAN (PODARCIS-SICULA-SICULA) OVARIAN FOLLICLES AT DIFFERENT DEVELOPMENTAL STAGES

Prostaglandin F2alpha (PGF2alpha), prostaglandin E2 (PGE2), progestero ne, androgens, and estradiol-17beta in vitro basal release by follicle s of the oviparous lizard, Podarcis s. sicula was studied; in addition , the in vitro effect of PGF2alpha and PGE2 on sex steroid release was evaluated. Follicles were divided according to the different vitellog enic developmental stages: pre-vitellogenic, early-vitellogenic, mid-v itellogenic and fully-grown. PGF2alpha and progesterone basal release was highest in fully-grown follicles; PGE2 and estradiol basal release was highest in early-vitellogenic follicles; androgens basal release was detectable in mid-vitellogenic and fully-grown vitellogenic follic les only. PGF2alpha increased progesterone release by fully-grown foll icles; PGE2 increased estradiol release by all follicle types, except by early-vitellogenic ones. The present data suggest that PGF2alpha an d PGE2 exert different roles on follicles: PGF2alpha seems to induce o vulation through the mediation of progesterone, while PGE2 seems to be implied in the start and the sustaining of oocyte vitellogenic develo pment through the mediation of estradiol.