Expression of the serotonin transporter SERT in the genital tract of cattle

Both prostate and vestibular glands of mammals contain neuroendocrine cells which synthesize, store and release growth factors including neuropeptides and biogenic amines such as serotonin. An increase of the secretory products by these cells has been correlated to tumour progression and poor prognosis. Serotonin mediates a wide range of physiological functions by binding to multiple receptors on cell surface. However, the entire serotonergic system is mainly regulated by the serotonin transporter SERT which modulates serotonin concentration in extracellular fluid. Primarily located in serotonergic neurons, SERT is also expressed in various cell types in the periphery. In this study, we found a wide distribution of SERT in the parenchymal cells of both the prostate and the vestibular glands of cattle using immunohistochemistry. The expression of SERT mRNA transcripts was assessed by reverse-transcription polymerase chain reaction, thus suggesting that SERT is locally synthesized. Furthermore, Western blotting analysis showed the presence of two isoforms of the protein (70 and 140 kDa), probably corresponding to the high mannose-type SERT and its dimeric form. Our results provide the first evidence for SERT expression in the mammalian genital tract, thus highlighting a new potential target for the therapy of the genital tract cancers.