Induction of steroid 21-hydroxylase/beta-galactosidase transgene expression by unilateral adrenalectomy

Unilateral adrenalectomy was used to induce compensatory growth in the contralateral adrenal gland of transgenic mice bearing a steroid 21-hydroxylase promoter/beta-galactosidase reporter (21-OHase/beta-gal) transgene, in which 6.4 kb of 5'-flanking sequence of the mouse steroid 21-OHase A gene are linked to a LacZ reporter gene. 48 hours following removal of the right adrenal gland, the left gland of transgene-positive mice showed a 4.5 fold increase in specific activity of the beta-gal reporter, compared to the right gland, while left glands from sham-operated transgene-positive and unilateral adrenalectomized transgene-negative mice showed no such increase. The increased specific transgene reporter activity, relative to total adrenal gland protein, must result from up-regulation of transgene expression, rather than from the compensatory increase in adrenocortical mass. This suggests that elements regulating trophic hormone-mediated 21-OHase gene expression in vivo are located within 6.4 kb of the 21-OHase gene transcription start site.