Physiology of the prostate.

The presence of the prostate is universal in mammals; when compared among species the prostate is marked by variations in its anatomy, biochemistry and pathology. The epithelial cells provide secretions that empty through ducts into the urethra to form a major component of the seminal plasma of the ejaculate. The prostate is stimulated to grow and is maintained in size and function by the presence of serum testosterone. Several protein-type growth factors, such as urogastrone and prostatropin, may also affect prostatic growth. After testosterone from the plasma has entered the prostatic cell through diffusion it is metabolized to other steroids by a series of enzymes. Over 95% of testosterone is converted to the most important prostatic androgen dihydrotestosterone. DHT then binds to the activated androgen receptor. The hormone receptor complex undergoes transformation and translocation into the nucleus. In the nucleus RNA-polymerase is activated followed by the synthesis of mRNA. The noncellular stroma and connective tissue compose the extracellular matrix. The extracellular matrix plays an important role in development and control of cellular functions.