IMMUNOHISTOCHEMICAL LOCALIZATION OF STEROID 5-ALPHA-REDUCTASE-2 IN THE HUMAN MALE FETAL REPRODUCTIVE-TRACT AND ADULT PROSTATE

The activity of the type 2 isozyme of steroid 5 alpha-reductase is cru cial for normal development of the external genitalia and prostate in human males. We used immunohistochemisty to localize type 2 isozyme ex pression in the human male fetal reproductive tract and adult prostate . In fetal tissue, the stroma of the seminal vesicles, corpus cavernos um, corpus spongiosum, dorsal vein complex, scrotal skin, and prostate expressed the enzyme. In addition, the epithelial cells of the fetal urethra and proximal prostatic ducts stained positively. The type 2 is ozyme could not be detected in epithelial cells of the fetal prostatic acini, seminal vesicles, prostatic utricle, ejaculatory ducts, epidid ymides, and Cowper's glands. Adult prostate specimens were derived fro m transurethral prostatectomies performed for benign prostatic hyperpl asia. Enzyme expression in these benign prostatic hyperplasia samples localized to the stroma and epithelial cells of the urethra and proxim al ducts. No staining was detected in the acinar (luminal and basal) e pithelial cells. Double staining with an antismooth muscle actin antib ody localized type 2 isozyme expression to the stromal fibroblast cell s of the prostate. Double staining with an androgen receptor antibody localized AR expression to the acinar epithelial cells and stromal fib roblasts. These data indicate that 5 alpha-reductase type 2 is express ed throughout the developing male genitourinary tract and functions as both an autocrine and a paracrine mediator of growth and differentiat ion.