Abstract
Follicular atresia is closely related to both apoptosis and autophagy of granulosa cells (GCs) in ovarian follicles. In the present study, GCs were isolated from pig ovaries in small, medium and large antral follicles, and the current results showed that the proliferation of GCs was higher in medium follicles, and lower in large follicles compared to small follicles. The Bax and Caspase 3 mRNA levels were significantly higher, but the ratio of Bcl-2/Bax was lower in GCs of large follicles. The marker genes of autophagy, Atg3, Atg7 and LC3 mRNA levels were higher in GCs from medium follicles. Apoptosis- and autophagy-related proteins had a similar expression pattern to the mRNA level. Our results showed that phosphorylated ERK (p-ERK) was activated in GCs of large follicles, while phosphorylated AKT (p-AKT) and phosphorylated mTOR (p-mTOR) were inhibited in GCs of medium follicles. Labeling of autophagic vesicles with 4',6-diamidino-2-phenylindole (DAPI) and monodansylcadaverine (MDC) confirmed the results of gene transcription and protein expression in GCs of different size follicles. We conclude that autophagy and apoptosis of GCs occurred in different size follicles during follicular development, and autophagy was mainly found in GCs of medium follicles, while apoptosis was mainly found in GCs of large follicles.