An androgen-responsive human prostatic cell line, LNCaP, was examined for the expression of mRNAs encoding the inhibin/activin subunits and activin receptors as determined by reverse transcription polymerase chain reaction (RT-PCR) and hybridization. Messenger RNA of the beta A- and beta B-subunits of inhibin/activin and activin receptors I, II, and IIB were expressed in these cells. The specificity of the RT-PCR products was confirmed by DNA sequencing. However, the expression of the alpha subunit of inhibin was not observed. In addition, activin proteins were localized immunocytochemically in the cytoplasm of LNCaP cells. The expression of both activins and activin receptors in LNCaP cells suggests that activin may have an autocrine function in these cells. Since activin acts as a modulator of cell proliferation and differentiation in many biological systems and inhibin possesses antagonistic actions to those of activin, it is proposed that the proliferation of LNCaP cells may be associated with an imbalance between the expression of activins and inhibins.

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