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CONVERSION OF P 5TO P4 ON FOLLICULAR COMPONENTS AND ITS ROLE IN MATURATION OF R. arenarum OOCYTEArias Torres AJ,P¨¢ez JB, Ajmat MT, Zelaray¨¢n LI.InstitutoSuperior de Investigaciones Biol¨®gicas (INSIBIO), CONICET-UNT. Fac. de Bqca., Qca. y Fcia. Tucum¨¢n. anajoarias@hotmail.com The two-cell model was proposed todescribe ovarian steroidogenesis in Ranasp. In contrast, this process also includes the participation of the oocytein X. laevis. There is no data aboutsteroid biosynthesis in the components of the ovarian follicle of R. arenarum. The aim of this work was torecognize follicular components and to analyze the conversion of pregnenolone(P5) to progesterone (P4) in each of them.Pieces of R. arenarumovary were histologically processed and stained with H-E and Mallory trichrome.Ovarian follicles components were separated by microdissection (complete follicles= CF, without theca follicles = WTF, follicular cells= FC, theca = T and nakedoocytes = NO) and P4 synthesis was measured in all of them by ECLIA.Determinations were carried out at: baseline, gonadotropin stimulation (hCG 10IU / mL) and in presence of P5 (100 ng / mL). Reinitiation ofmeiosis (GVBD) was monitored.Topographical stains allowed to observe that the CFare formed by a NO surrounded by a single layer of FC and a thin layer ofconnective tissue which corresponds to T. All the components secreted < 1nM ofP4 at baseline, except for the CF (¡Ö 2.4 nM) and GVBD was not found.P4 secretion increased significantly in CF (¡Ö 80 nM) understimulation with hCG and it increased in all components (¡Ö 50-80 nM) in thepresence of P5 and the oocytes matured.These data suggest that the main source of P4is the follicular cells. The oocyte could be engage in this process or be areservoir of this steroid in the R.arenarum ovary.