Histological characterization and in situ localization of apoptosis in thepig follicular atresia

The aim of this study is the histological characterization of the atretic p rocess of follicles in pig ovary. Two mechanisms have been found. In the at retic preantral follicles changes are produced in the oocyte, in the granul osa cells, an in the newly formed theca. Three histological phases can be d istinguished during atresia in preantral follicles. The principal observed modification is the loss of the connections among granulosa cells that acqu ire a star-shaped aspect. Few apoptotic cells were observed. In the atretic antral follicles four histological phases were characterized. The presence of apoptotic cells increases progressively in the first three. A peculiar distribution of apoptotic cells in the granulosa as well as in the theca we re observed in all phases. In conclusion: A) During atresia of antral folli cles in porcine many apoptotic cells were observed in the granulosa and in the theca. B) Very few apoptotic cells were found during atresia in the pre antral follicles. The possible existence of some other cell death mechanism different from apoptosis which may participate in the atresia of this type of follicles is proposed.