Ultrastructural studies of the bovine Graafian Follicle and corpus luteum

Ovaries were obtained from normal adult dairy cows at all days of the estrous cycle. The largest Graafian follicle and corpus luteum were excised and prepared for electron microscopic study. In the follicle wall, membrana granulosa cells contained granular endoplasmic reticulum and mitochondria with villous or lamellar cristae. The theca interna cells during proestrus and estrus contained ribosomes separated from endoplasmic reticulum. The latter during these periods assumed tubular and tortuous shapes. Mitochondria during these periods assumed rounded shapes, were occasionally cup-shaped, and developed tubular cristae. In the corpus luteum, the large luteal cells during metestrus and diestrus contained an abundance of agranular, tubular, branching membranes of endoplasmic reticulum and Golgi apparatus. Mitochondria were large, with tubular cristae, but smaller mitochondria, with irregular or villous cristae, were also present. 'Transitional bodies' of the latter mitochondria to another form were observed. Cup-shaped and annular mitochondria were present during diestrus. In the small luteal cells, large vesicular membrane formations were present and often associated with lipid bodies. The cells were lipid-laden. Lysosomes and granular bodies were present during luteal regression. The observed features of the granulosa cells are related to protein synthesis, those of the pre-ovulatory theca interna cells and metestrus-diestrus large luteal cells to steroid synthesis, and those of the small luteal cells to lipid storage.