Estrogenic Regulation of Uterine 90-Kilodalton Heat Shock Protein *

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Abstract
Recently two lines of evidence have implicated that cellular heat shock proteins (hsp) may play a role in steroid hormonal regulation of target tissues. One is the demonstration that cellular 90K hsp (hsp-90) can complex with steroid receptors in vitro and inhibit their ability to interact with DNA, and second, the demonstration that an avian oviduct sex steroids can regulate the synthesis of hsp-108. As yet, there is no report that sex steroids can regulate hsp-90 synthesis, especially in mammalian tissues. In these studies we have examined the estrogenic regulation of murine uterine hsp-90. We report that ovariectomy reduces the uterine concentration of hsp-90, and estradiol causes a time-dependent increase in uterine bsp-90 as early as 4 h after steroid administration, reaching a maximum increase of 4-fold between 18-24 h. The effect is specific to estrogens and not elicited by other steroid hormones. It is also target tissue specific, such that it is seen with uterus and vagina and does not occur in nontarget tissue for estradiol, such as spleen. The possible physiological significance of estrogenic stimulation of uterine hsp-90 has been discussed.