Effects of culture conditions on the growth and differentiation of transformed rat adrenocortical cells.

Normal rat adrenocortical cells grow in vitro in two states of differentiation, depending on culture conditions. Under one set of conditions, they proliferate and are fibroblast shaped, with some myoid cell characteristics and with limited steroidogenic activity. Under alternate conditions they do not replicate and are epithelial-like and similar to adrenocortical secretory cells structurally and steroidogenically. The effects of oncogenic transformation on these cellular responses to culture variables were examined by using the Kirsten murine sarcoma virus-transformed rat adrenocortical line TRA. Transformation eliminated the differential proliferative response of the cells to culture variables and resulted in similar growth rates and high cell densities under all conditions. Horse serum, conducive to epithelial-like growth of nontransformed cells, caused aggregation, whereas fetal calf serum, conducive to fibroblastic growth of untransformed cells, caused dispersed growth in TRA cultures. Variations in dissociation procedures had little effect on growth patterns. Most ultrastructural characteristics of myoid as well as adrenocoritcal differentiation were reduced in TRA cells, although basement membranes and extracellular matrix were produced, but under different conditions than in untransformed cultures. Like normal adrenocortical cells, TRA cells were capable of 20alpha-reduction and delta5-3-beta-dehydrogenation of [4-14C5pregnenolone but, in contrast to untransformed cells, they did not respond to variables in culture conditions by qualitative changes in pregnenolone metabolism, did not produce deoxycorticosterone or corticosterone, and secreted progesterone, a hormone not recovered from untransformed cultures. TRA cells showed no increase in steroidogenic differentiation in response to those culture environment factors that normally cause modulation of the fibroblast-shaped adrenocortical stem cells to more differentiated steroid-secreting cells.