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 hor mone (PRL-GB), including placental lactogen (PL) and placental prolactin li ke protein (PLP), during pregnancy, It is important to study placental loca l regulators that control the expression of PRL-GH genes, We have previousl y 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 r eceptor 1a (MeI1a) and the effects of DA and melatonin on the expressions o f PL-Iv, PL-II, PLP-C genes and Pit-1 gene that are involved in the express ion of PRL-GH genes in the rat pituitary and placenta. According to the Nor thern 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 th e 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, ch loromelatonin in culture media also decreased the levels of PL-IV, PL-II an d PLP-C mRNA, However, melatonin does not affect the Pit-1 mRNA level, Thes e data suggest that D-2 and MeI1a may control the expression of PRL-GH gene s in the rat placenta and its response to the extracellular changes of DA a nd melatonin secreted from the maternal organ. However, Pit-1 may not be in volved in the MeI1a induced inhibition of PRL-GH gene expressions in the ra t placenta.