Steroidogenesis expression depends on negative control(s): analysis in Leydig × adrenal intraspecific cell hybrids

Abstract Hybrids constructed by fusing mouse Leydig cells with mouse adrenal Y 1 cells were able to randomly express all the parental specific traits but for the response to gonadotropin (hCG) and corticotropin (ACTH): three of them, YDYL 14, 17 and 19, metabolized both progesterone and dehydroepiandrosterone into testosterone accounting for 17α-hydroxylase, 17–20-lyase, 17-ketoreductase and 3β-hydroxysteroid dehydrogenase activities. Under basal conditions, 17α-hydroxylase and 17–20-lyase activities were high in the three clones as compared to parental Leydig cells, and were no longer stimulated by cAMP in YDYL 17 and 19. The hybrids responded to various hormones such as prostaglandin E 2 (PGE 2 ), vasoactive intestinal peptide (VIP) and prolactin (PRL) which are not directly implicated in the expression of Steroidogenesis; they generally retained the Y 1 morphological response to 8-bromo cAMP. On extended culture, reexpression of ACTH sensitivity occurred in one clone, YDYL 9. This reexpression was correlated with a Robertsonian translocation between mouse chromosomes 2 and 11, while extinction required the presence of an intact mouse chromosome 11.