Steroidogenic and morphological responses of hen granulosa cells to luteinizing hormone in vitro.

We examined in vitro progesterone production in granulosa cells isolated from the first (F1 group, 35 mm diameter) and third (F3 group, 25 mm diameter) largest ovarian follicles and granulosa cells isolated from hens stimulated hormonally to produce multiple follicular maturation (PMSG group). All granulosa cell groups maintained in a 48 hr culture produced progesterone. Luteinizing hormone (LH) significantly increased progesterone production for each group with the PMSG group progesterone levels the highest and F3 group the lowest. Light and scanning electron microscopy revealed that few single granulosa cells were present after 48 hr culture. Instead, granulosa cells were observed as multicellular aggregates, referred to here as clusters, which ranged between 15 and 60 micron in diameter. Regardless of the cell group few clusters attached to a support surface. The surface of F1 and PMSG clusters were irregular due to short folds and formed few surface elaborations. Individual cell boundaries within a cluster could not be discerned. With LH, surface folds became more elaborate, often giving rise to microvilli. Blebs about 1 micron in diameter or less also were more prevalent on clusters from groups cultured with LH. Clusters within the F3 group cultured with and without LH were similar in appearance. Therefore, in the F1 and PMSG groups, the development of surface elaborations in the form of microvilli and blebs was correlated with the LH promoted increase in progesterone production.