Estrogenic regulation of HSP90 kD synthesis in rat urinary bladder

The role of heat shock protein (HSP90 kD) has been investigated in regard to its association with steroid receptors. HSP90 kD may play a role in steroid receptor stabilization and activation. Oophorectomized Sprague-Dawley rats (n = 25) were placed into five groups and injected subcutaneously with 30 microg beta-estradiol 17-benzoate in sesame oil, with one group injected with carrier oil (control). After estrogen administration, the rats were killed, and their bladders removed for immunostaining, immunoblotting and enzyme-linked immunosorbent assay (ELISA). Immunoblot analysis demonstrated a 90-kD band in bladder homogenates, even in the absence of estrogen. However, the bands were more intense 12 and 24 h after administering estrogen. ELISA showed significant differences in HSP90 kD synthesis as early as 6 h compared to controls (P< 0.05). After 48 h the estrogen-treated rats and controls were identical. The above results were confirmed by immunostaining for HSP90 kD. HSP90 kD synthesis in the rat urinary bladder is under estrogenic regulation. These findings may be relevant in the etiology and pathobiology of interstitial cystitis and menopausal voiding dysfunctions since the bladder is enriched with estrogenic receptors and is under estrogenic influence.