ULTRA-STRUCTURAL CHARACTERISTICS OF BOVINE GRANULOSA-CELLS ASSOCIATEDWITH MAINTENANCE OF ESTRADIOL PRODUCTION IN-VITRO

We investigated whether the maintenance of oestradiol production by bo vine granulosa cells (GC) in vitro was related to GC ultra-structure, and studied the effects of inclusion of serum as a cell attachment fac tor on oestradiol secretion, cell morphology and ultra-structure. Bovi ne granulosa cells from medium-sized follicles (4-8 mm diameter), in a serum-free (SF) culture system, maintained oestradiol production for 6 days, whereas oestradiol secretion by cells cultured in serum-coated (SC) wells declined rapidly with time, in culture. SF cells formed cl umps consisting of two types of cells. Cells within dumps presented a phenotype similar to GC in vivo, being spherical, tightly joined by ex tensive gap junctions and interdigitated pseudopodia/microvilli, had a bundant rough and smooth endoplasmic reticulum (ER) and mitochondria w ith trabecular cristae. In contrast, cells cultured in either SC wells or in the flattered base of cell clumps from SF cultures were enlarge d, containing less rough ER, had fewer mitochondria (which tended to b e round) and contained endosome-like structures, morphological charact eristics suggestive of early luteinisation. (C) 1997 Elsevier Science Ireland Ltd.