Immunohistochemistry and molecular biology studies of apelin and apelin receptor in queen placenta.

Placenta is a tissue where vasculogenesis, blood pressure and blood flow are dramatically important to allow normal embryonic and foetal growth and requires the production of numerous growth factors, hormones and transcription factors. Apelin is a pleiotropic peptide, and its major action relates to energy metabolism, cardiovascular function, body fluid homeostasis via its receptor. The involvement of the apelinergic system during pregnancy in veterinary medicine has been investigated only in bitches. Thereafter, the aim of our study was to investigate, for the first time, presence and distribution of this system in the queen placenta at mid- and end-gestation. Ten pregnant mixed-breed queens were used. The animals were equally divided into two groups based on the stage of pregnancy (mid and end gestation) and, with the written consent of their owners, were subjected to ovariohysterectomy or non-conservative caesarean section. The Real-Time PCR (RT-PCR) analysis showed the presence of transcripts for apelin and its receptor in all the foetal and maternal placenta samples processed. The immunohistochemical (IHC) study evidenced the presence and the distribution of positive immunoreactions for apelin and its receptor in all the samples observed. In particular, in the placental labyrinthic portion, apelin and apelin receptor immunopositivity was evident in the cytoplasm of trophoblasts and endothelial cells. The uterine glands also exhibited a positive immune reaction for apelin and corresponding receptor. Based on our results, apelin and its receptor, also in the queen placenta, could be an important system involved in the physiological development of placenta, embryo and foetal growth.