Effects of mepartricin, a polyene macrolide antibiotic, on estrogen-induced hyperplastic growth of the dorsolateral prostate and seminal vesicle in immature castrated rats

Abstract

To investigate the effects of mepartricin, a polyene macrolide antibiotic, on estrogen-induced hyperplastic prostate and seminal vesicle (SV) growth in castrated rats. Immature rats aged 3 weeks were castrated and left untreated for 1 week. Then, 17beta-estradiol benzoate (E(2)-BA) was subcutaneously injected at a dose of 10 microg/day twice weekly, and mepartricin was orally administered at doses of 2.5, 5 and 10 mg/kg once daily for 3 weeks. The weights and hydroxyproline contents of the prostate and SV, the activity of growth factors (GFs) in the dorsolateral prostate (DLP) and the serum estrogen level were measured. Histological examination of the prostate and SV was also performed. Mepartricin dose-dependently suppressed the increase in the serum estrogen level, the weights and hydroxyproline contents of the DLP and SV and the elevation of GF activity in the DLP induced by E(2)-BA treatment. Histological examination also revealed that treatment with mepartricin reduced collagen accumulation and thickening of the smooth muscle layer in the DLP and SV, and proliferation of the glandular epithelium in the DLP. These results suggest that mepartricin suppresses hyperplastic growth of the DLP and SV induced by estrogen in immature castrated rats, the underlying mechanism being a reduction in the serum estrogen level, thereby suppressing stromal cell proliferation and activation.