Localization of angiotensin-converting enzyme in the human prostate: pathological expression in benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is the most common hyperplastic disease in man and it is characterized by increased cellular growth (stromal and epithelial hyperplasia) and enhanced local sympathetic tone, both of which are known to be augmented by activation of the renin–angiotensin system (RAS) in other tissues. Angiotensin‐converting enzyme (ACE) is an integral component of the RAS that is responsible for the production of the active peptide angiotensin II from the inactive precursor angiotensin I. The present study was undertaken to map the anatomical localization of ACE protein and messenger ribonucleic acid (mRNA) in the normal human prostate and to establish whether their expression is pathologically altered in BPH. Human prostate samples were obtained at post‐mortem and histologically defined as normal or hyperplastic. ACE protein binding/expression was determined by in vitro autoradiography and immunohistochemistry using the ACE‐specific radioligand [125I]‐MK351A and a mouse anti‐ACE polyclonal antibody, respectively, whereas the spatiotemporal distribution of ACE mRNA was determined by in situ hybridization using 35S‐labelled oligonucleotide probes. ACE protein was localized to the glandular epithelium in the human prostate. ACE binding and immunostaining were increased in BPH compared with normal (non‐hyperplastic) prostate specimens [X‐ray film autoradiography: normal 873±48 dpm/mm2 (n=8) vs. BPH 1631±274 dpm/mm2 (n=6), p