Effect of kisspeptin and RFamide-related peptide-3 on the synthesis and secretion of LH by pituitary cells of pigs during the estrous cycle

Abstract Actions of kisspeptins (KISSs) and RFamide-related peptide-3 (RFRP-3) at the hypothalamus modulate female reproduction. The action of KISS and RFRP-3 in the pituitary gland of pigs during the estrous cycle has not yet been delineated. The present study was conducted to assess the effect of KISS and RFRP-3 on relative abundance of αGSU and βLH mRNA transcript and LH secretion in vitro by pituitary cells of gilts during the estrous cycle. The cells were isolated from gilts on Days 2–3, 10–12, 15–16 and 19–20 of the estrous cycle and cultured in vitro without inclusion of GnRH (control) or with GnRH (100 ng/ml), KISS (10−6 M, 10−7 M) and RFRP-3 (10−6 M, 10−7 M) alone or in combination. The relative abundance of α-GSU and β-LH mRNAs was examined. Treatment with KISS increased the synthesis and/or secretion of LH by pituitary cells and RFRP-3 inhibited the synthesis and secretion of LH in the presence of GnRH on Days 10–12 and 15–16 of the estrous cycle. The synthesis and secretion of LH was greater when there was treatment with KISS and GnRH during the late follicular phase. Treatments with KISS and RFRP-3 affected the synthesis and/or secretion of LH during the luteal phase and luteolysis. In conclusion, KISS and RFRP-3 apparently affects the synthesis and secretion of LH by pituitary cells of estrous cyclic pigs. There appears to be a greater effect of KISS in modulation of LH secretion than RFRP-3 in pigs.