Quantitative ultrastructural analysis of the follicular and luteal cells of the bovine ovary

Ovaries were obtained from normal adult dairy cows at all days of the estrous cycle. The largest Graafian follicle and corpus luteum were excised, prepared for electron microscopic study, and their cell components quantitated using the linear scanning method and the counting of membrane crossings. The results indicated that in the theca interna cells during proestrus and estrus and in the large luteal cells during late metestrus and diestrus, enlarged mitochondria occupied an increased cytoplasmic percentage volume. During proestrus and estrus in the theca interna cells, the concentration of membranes of endoplasmic reticulum and Golgi apparatus also increased. The cytoplasmic percentage volumes of lipid bodies and of lysosomes increased in the small luteal cells; during luteal regression, they also increased in the large luteal cells. Similar rates of increase during follicular maturation, and decrease during luteal regression, occurred for measurements of succinic dehydrogenase and mitochondria. The quantitative observations were related to the production of steroid hormones by the ovary, and to the cyclic growth and regression of follicular and luteal cells. It was noted that an increased cytoplasmic percentage volume of mitochondria, an increased concentration of agranular cytoplasmic membranes, and low levels of lipid bodies and lysosomes, were generally present at times when ovarian steroid elaboration and cell growth were maximal.