PROSTAGLANDINS AND CORTICOSTERONE IN THE OVIPAROUS FEMALE LIZARD, PODARCIS-SICULA-SICULA, DURING REPRODUCTION

The in vitro effects of prostaglandin F-2 alpha (PGF(2 alpha)) and pro staglandin E(2) (PGE(2)) on corticosterone release by ovarian follicle s, corpora lutea (CL), and interrenaIs were studied in the female liza rd, Podarcis sicula sicula, during reproduction. Follicles and CL were divided according to their different developmental stages; follicles: previtellogenic, early-vitellogenic, mid-vitellogenic and fully-grown ; CL: CL1 (unshelled eggs in the oviducts), CL2 (shelled eggs in the o viducts), CL3 (eggs laid 6 h previously) and CL4 (eggs laid 48 h previ ously). Interrenals were divided according to the reproductive stages: pre-vitellogenesis, vitellogenesis, ovulation, post-ovulation, and po st-deposition. PGF(2 alpha) release was highest in fully-grown follicl es and PGE(2) in early-vitellogenic follicles, corticosterone was high est in pre-viteliogenic and lowest in early-vitellogenic follicles. PG E(2) decreased corticosterone in pre-vitellogenic, mid-vitellogenic an d fully-grown follicles. PGF(2 alpha) release was highest in CL4, and PGE(2) in CL1 and CL2, corticosterone was highest in CL4. PGF(2 alpha) increased corticosterone in CL1, CL2 and CL3. In interrenals, PGF(2 a lpha) release was highest and PGE(2) lowest during ovulation, corticos terone was highest during ovulation. PGF(2 alpha) increased and PGE(2) decreased interrenal corticosterone during vitellogenesis, ovulation, and post-ovulation. In the plasma, PGF(2 alpha) levels were highest a nd PGE(2) lowest during ovulation, corticosterone was highest during o vulation. These results suggest that corticosterone, modulated by PGF( 2 alpha) and PGE(2), is implied in the reproductive processes with dif ferent roles. In fact this steroid could favour ovulatory and luteolyt ic processes. In addition the hypothesis of an anti-vitellogenic role of corticosterone is discussed.