Inhibitory or stimulatory effect of human genes on the expression of adrenal function in human Leydig × Y 1 cell hybrids

Abstract

In order to investigate the expression and the regulation of steroidogenesis, human Leydig cells were fused with a functional mouse adrenal cell line (Y 1). Six independent hybrid clones were analysed for hormone receptors and for cAMP and steroid response to ACTH, hCG, 8Br-cAMP or forskolin. All hybrids had lost hCG receptors and their ability to produce testosterone. With respect to the response of adenylate cyclase to ACTH and/or forskolin, hybrids could be classed into two groups. In the first group, the pattern of response was qualitatively similar to Y 1 parental cells; The second group was far less responsive to ACTH than are Y 1 cells, and when added together, forskolin and ACTH only had an additive effect. All hybrids responded to ACTH and 8Br-cAMP with an increased production of pregnenolone (P 5). The amounts of P 5 produced both under basal conditions and following 8Br-cAMP stimulation were significantly higher in three hybrids when compared to y 1 cells. However, the ability of two of these three hybrids to produce 20α-dihydroprogesterone (20α OHP 4) was very low. The metabolism of [ 14C]P 5 revealed that in one of these hybrids, there was a loss of 3β-hydroxysteroid dehydrogenase/isomerase whereas in the other case, there was a low 20α-hydroxylase activity. The inhibition of cell growth by ACTH was related to the ability of the hormone to stimulate cAMP. Conversely, the inhibitory growth effects of 8Br-cAMP were not always inversely correlated with the ability of this nueleotide to stimulate P 5 production. Since hybrids contained two mouse genomes and retained variable human chromosomes, these results suggest that extinction or enhancement of murine genes coding for some of the enzymes involved in steroidogenic response to ACTH was due to the regulation by human genes.