Effect of a Gonadotropin Releasing Hormone Agonist on Rat Ovarian Follicle Steroidogenesis and Apoptosis

TESONE, M; PARBORELL, F; IRUSTA, G; GONZALEZ, OM; VITALE, AM; ABRAMOVICH, D; PELUFFO, MC; CALANDRA, R

Philadelphia, Pennsylvania

Congreso; 85th Annual Meeting of the Encocrine Society; 2003

Endocrine Society

The purpose of the prescnt study was to evaluate the in vivo effect of the GnRH analogue leuprolide acelate (LA) on steroidogenesis, follicular development and apoptosis-related mechanisms in preovulatory ovarian follicles (POF) obtained from prepubenal eCG-treated rats. Rats received a single dose ofeCG with or without LA (0.5 ughat) repeated every 12 h during 48 h and then sacrificed. Treatment with LA resulled in a significant increase in follicular progesterone levels, whereas a significant decrease in androgen (testosterone and androslerone) and eSlradiollevels was observed. Similar results were oblained when serum androgens and eSlradiol were measured, but serum progesterone levels were unchanged. Ovarian histology revealed an inhibitory effect of LA treatment on the follicular development induced by eCG; Ihe numbers ofatretic and preantral follicles were increased as compared wilh eonlrols, whereas the number of anlral follicles had decreased. Cells undergoing DNA fragmentation were qnantified by performing in situ 3´ end labeling of DNA with digoxygenin-dUTP on ovarian seclions; LA treatment caused an increase in Ihe percenlage of apoptolic cells in preanlral and antral follicles. La trealed rals showed a significant increase in the spontaneous onset ofapoptolic fragmentalion ofDNA isolaled from POF and incubaled 24 h in serum-free medium. Follicular contents ofBcl-2, Bax and Bcl-x proteins were measured by Western blolling. POF oblained from LA´treated rats showed no changes in Bcl-2 or Bax protein levels. However, a reduction in the Bcl-xL:Bcl-xS ratio was observed, with a greater decrease in Bcl-xL compared with Bcl-xS during the incubalion, suggesting a lower stabilityofthe Bcl-xL isoform in the LA group. In addilion, immunoslaining for Bax and Bcl-2 was studied in ovarian cells. Bax immunoreactivity was intense in peri-antral granulosa cells, but was diffusely expressed in mural granulosa cells. (n theca cells, Bax . staining was lower Ihan in granulosa cells. Wilh regard 10 Bcl-2, it was localized diffusely in granulosa cells and more intense in theca cells. These results indicate thai in vivo GnRH agonist treatment produces an inhibitory effect on ovarian androgen and estradiol production and an increase in the apoplosis process in ovarian follicles oblained from eCG-trealed rats. Supported by ANPCYT (PICT 6384 BID 1201 OC-AR), UBA (01ITW05, University of Buenos Aires, Argentina).