The effect of 5alpha-dihydrotestosterone (DHT) on the level of human prostatic acid phosphatase (hPAP) mRNA was studied using tissue slices from various benign prostatic hyperplastic glands. The absence of DHT in the incubation medium led to a gradual, significant decrease of the hPAP mRNA level. Addition of the hormone induced hPAP mRNA in a time- and dose-dependent manner. The maximal 2-4-fold induction by 10(-9) M DHT was observed after 3-5 h of incubation, and then the hPAP mRNA level was 6-20-fold higher than that in a parallel sample incubated without DHT. The results suggest that DHT is necessary to sustain the expression of hPAP in hyperplastic prostates.