Morphometric analysis of in vivo development of porcine ovarian granulosa cells in preovulatory antral follicles.

Granulosa cells (GC) from immature (1-2 mm), developing (3-5 mm), and preovulatory (6-12 mm) antral porcine follicles were examined by stereological, ultrastructural techniques. Partial cell volumes occupied by nuclei or mitochondria did not differ significantly as follicles enlarged. Whorled smooth endoplasmic reticulum (ER) increased significantly in large follicles compared to either small or medium sized follicles. Whorled rough ER elements were present in similar amounts in small and medium sized follicles and absent in large follicles. The GC of large follicles contained significantly more lipid and Golgi complexes than that of small follicles, but the lipid and Golgi complex content of GC from medium follicles was not significantly different from that of either small or large follicles. Proportions of total cell volumes occupied by lysosomes and multivesicular bodies increased as follicular size increased. This confirms earlier qualitative studies, and provides a quantitative in situ basis for future in vitro studies.