Androgen regulation of a specific gene in hamster flank organs.

Flank organs of Golden Syrian hamster containing large sebaceous glands are a useful model for studying androgen-dependent gene expression. Recently, we have isolated an androgen-dependent gene from a cDNA library constructed from male mRNAs of flank organs. In the present study, using this gene as a probe, we examined the kinetics of loss and re-expression of the mRNA of this gene. Dot blot hybridization, the current method, can approximately quantify mRNA levels. Castration caused a marked decrease in the mRNA within a few days to undetectable levels. Topical application of testosterone re-activated the mRNA levels, with the earliest activation within 24 h. The results of various topical steroid applications showed a full re-activation of the mRNA by testosterone and dihydrotestosterone, partial re-activation by androstanedione and androstenedione, and no activation by androstanediol or dehydroepiandrosterone. Simultaneous application of testosterone and progesterone inhibited the expression of mRNA but application of dihydrotestosterone and progesterone did not. The current dot blot hybridization technique appears to be a more direct approach for studying androgen action on DNAs than other previously used methods such as morphometry or enzyme assay.