Effects of dopamine and melatonin on the regulation of the PIT-1 isotype, placental growth hormone and lactogen gene expressions in the rat placenta

Rat placenta produces several members of the placental prolactin-growth hormone (PRL-GB), including placental lactogen (PL) and placental prolactin like protein (PLP), during pregnancy, It is important to study placental local regulators that control the expression of PRL-GH genes, We have previously reported that dopamine (DA) can regulate Pit-1 and PL-II gene expressions. In this study we aimed to investigate the local expression of melatonin receptor 1a (MeI1a) and the effects of DA and melatonin on the expressions of PL-Iv, PL-II, PLP-C genes and Pit-1 gene that are involved in the expression of PRL-GH genes in the rat pituitary and placenta. According to the Northern blot analysis, DA receptor 2 (D-2) was expressed in the rat placenta. We also report on the local expression of MeI1a in the rat placenta for the first time. Injected DA agonist, bromocriptine (in vivo) decreased PL-Iv, PLP-C and Pit-1 mRNA levels in the rat placenta, The melatonin agonist, chloromelatonin in culture media also decreased the levels of PL-IV, PL-II and PLP-C mRNA, However, melatonin does not affect the Pit-1 mRNA level, These data suggest that D-2 and MeI1a may control the expression of PRL-GH genes in the rat placenta and its response to the extracellular changes of DA and melatonin secreted from the maternal organ. However, Pit-1 may not be involved in the MeI1a induced inhibition of PRL-GH gene expressions in the rat placenta.