The purpose of this study was to determine whether DU145, a human prostate cancer cell line: (a) transcribes mRNAs coding for beta A- and beta B-subunits of activin, a member of transforming growth factor beta (TGF beta) superfamily, and activin receptors I, II, and IIB; and (b) produces activin proteins. The expression and localization of the mRNAs were elucidated by the reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization techniques. The production of activin was determined by immunocytochemistry. We have observed that messenger RNAs encoding activin beta A-, beta B-subunits, and activin receptors I, II, and IIB, but not that of the alpha-subunit of inhibin, were expressed, and activin proteins, but not inhibin, were produced, by DU145 cells. Furthermore, the RT-PCR products were confirmed by DNA sequencing. It is concluded that activins and their receptors are expressed in DU145 and activins may have autocrine functions in DU145 cells.