Pharmacological and molecular evidence for the expression of the two steroid 5α‐reductase isozymes in normal and hyperplastic human prostatic cells in culture

BACKGROUND Whereas the embryological development of the human prostate is clearly dependent on steroid 5α‐reductase (5α‐R) type 2 expression, the respective expression of the two known isoforms (types 1 and 2) of 5α‐R in the adult human prostate remains unclear. METHODS 5α‐R isoform mRNA expression (Northern blots and reverse transcriptase‐polymerase chain reaction [RT‐PCR]) and enzyme activity were studied in immortalized epithelial cells (NE) and in fibroblasts from normal (NF) or hyperplastic (BPHF) human prostates. RESULTS 5α‐R activity (fmol/μg DNA/hr) was 1.43 ± 0.5 in NE, 10.7 ± 4.7 in NF, and 79 ± 37 in BPHF. mRNAs for both 5α‐R isoforms were expressed in the three cell types, as shown by Northern blot and RT‐PCR analysis. LY306089, a selective 5α‐R type 1 inhibitor, strongly inhibited 5α‐R activity in all cell types (IC 50 : 10 nM), confirming the predominant expression of 5α‐R type 1 in these cells. Finasteride, a 5α‐R type 2 inhibitor, was less efficient (IC 50 : 45, 35, and 65 nM in NE, NF, and BPHF, respectively). In addition, the inhibition by finasteride decreased with serial subculture in NF only, suggesting an effect of age in culture on the expression of 5α‐R type 2 in these cells. SKF105657, also a 5α‐R type 2 inhibitor, was a poor inhibitor in this system. CONCLUSIONS These studies demonstrate that human prostate cells in culture express both isoforms of 5α‐R and suggest a balance in the expression of the two isoforms as a function of various regulatory factors. Prostate 32:155–163, 1997. © 1997 Wiley‐Liss, Inc.