Adebayo Koyuum Akinloye & Bankole Olusiji Oke

Summary

Fine structures of the ovary during the oestrous cycle in African giant rats (Cricetomys gambianus Waterhouse) were described in the present study. Ultrastructural features of the germinal epithelium and the medullar of the ovary were similar at different stages of the oestrous cycle. During mid proestrus, there was disorganization of the inner layer of the granulosa cells of secondary follicles to form the antrum. At late proestrus/early estrus, antrum formation had advanced and there was evidence of reorganization of granulosa cells. Fine structures of the ovary during mid estrus include follicles with variably shaped mitochondria, profiles of Golgi complexes and dense concentration of ribosomes. The theca interna shared similar ultrastructure with the granulosa cells containing, in addition, lipid droplets and smooth endoplasmic reticulum. Cellular ultrastructure observed during mid metestrus showed commencement of differentiation of corpus luteum. At mid diestrus, the general ultrastructural architecture of the ovarian follicles showed disorganized cellular contents and corpus luteum was recognized with conspicuous depolarization of the basement membrane originally separating granulosa cells from the theca. At late diestrus/early proestrus, granulosa cells displayed numerous mitochondria of variable sizes and shapes. Ribosomes were evenly distributed throughout the cytoplasm while electron lucid vesicles were sparsely distributed. The results of this study showed that fine structural changes in the ovary of the giant rat during the oestrous cycle are similar to those of laboratory rodents.

KEY WORDS: Ultrastructure; Ovary; Oestrous Cycle; African Giant Rat.

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