Hormonal regulation of FHG22 mRNA in Syrian hamster harderian glands: role of estradiol.

The regulation of the FHG22 gene by sex steroids has been studied in Syrian hamster Harderian gland, an organ with sexual dimorphism in which the FHG22 mRNA is female-specific. Testosterone treatment of females caused irregular inhibitory effects on the FHG22 mRNA levels, whereas male castration originated transitory increases during less than 2 weeks. Treatment of 15 day-castrated males for 1 or 2 days with beta-estradiol-3-benzoate caused a marked stimulation in the FHG22 mRNA levels. The results found in vivo may be explained considering those found in female Harderian gland serum-free primary cell cultures. In the absence of hormones, the FHG22 mRNA levels decreased along the time and neither progesterone, testosterone, or 5 alpha-dihydrotestosterone affected the expression. However, estradiol stimulated the FHG22 mRNA expression in a time and dose-dependent manner: increasing effects were detected between 8-96 h of treatment and the EC50 was about 10(-9) M. The estradiol effect was reverted by the antiestrogen ICI 164,384 or by cycloheximide. We conclude that estradiol stimulates FHG22 mRNA expression in Harderian gland, although other agents may also control the expression in vivo.