CONICET | Buscador de Institutos y Recursos Humanos

Catecholamine secretion increases during stress, and breast cancer diagnosis generates distress to most patients. Another hormone that increases during stress is Prolactin (PRL), which exerts a mitogenic effect acting through the prolactin receptor (PRLR). PRL is also synthesized by normal and tumor breast tissue, giving place to an autocrin/paracrine loop. Previously, using the Nb2 bioassay we have shown that T47D cells increase PRL synthesis and release in the presence of a2-adrenergic agonists. Then, part of the mitogenic effect generated by adrenergics compounds could eventually be due to increased PRL synthesis by the cells. We have previously demonstrated a2-adrenoceptors (á2-RA) expression on T47D human breast cancer cells, associated with a mitogenic effect. Rauwolscine (RAU), an a2-adrenergic antagonist, behaved like an inverse agonist. The objective of the present work was to elucidate if different adrenergic compounds are able to regulate PRLR mRNA expression at the transcriptional level. RT-PCR assays of the long isoform of PRLR were performed. The cells were incubated with different adrenergic compounds: 1 or 10 nM Epinefrine (EPI) or Dexmedetomidine (DEX) in the presence or absence of 1 nM RAU. After treatment for 24 or 48 hs we extracted total RNA with TRIZOL and then RT-PCR assays were carried out. Western blotting and immunocitochemistry for the PRLR were performed. The expression of the long, intermediate and delta-S1PRLR isoforms of the PRLR was verified in the T47D cell line by immunocytochemistry and Western blotting. The receptors were more concentrated near the plasmatic membrane. The intermediate isoform was preferentially expressed by approximately 50% as compared to the rest of PRLR isoforms. Expression of mRNA for the long isoform of the receptor was observed in all treatments and times tested, the increase being approximately 50 % after 24 h with Epi 1 nM. The stimulation of T47D cell proliferation mediated by the á2-RA could be partly mediated by an increase in PRL synthesis and release by these cells but not by the regulation of the RNAm PRLR at the transcriptional level.