Endocrine Abstracts

The reproductive system is controlled by (GnRH) secretion from the brain, which is finely modulated by a number of factors, including gonadal sex steroids and inhibins. It was recently claimed that kisspeptin (KP) and gonadotropin inhibitory hormone (GnIH) neurons are regulators of GnRH secretion. Therefore, we have developed highly specific and sensitive fluoro-immunoassays (FIAs) using Eu-labeled antigens for KP 10 and GnIH. In this study, the distributions of KP 10 and GnIH in rat and ovine brains were determined by FIA, and they were compared those of GnRH.

Using Eu-labeled KP-10 and GnIH, highly sensitive immunoassays for KP-10 (IC50, 87 pg/ml) and GnIH (IC50, 15 pg/ml). After decapitation, rat and ovine brain tissues were boiled for 10 min in 1-N acetic acid, after which they were homogenized in 10 volumes (v/w) in 1-N acetic acid. Aliquots of supernatant were evaporated and dissolved well in assay buffer.

When the distribution of KP was examined in rat brain, KP was detected only in the hypothalamus (35 pg/100 mg wt), with negligible KP in other tissues. However, the amount of GnIH was high in rat brain; the highest concentration was found in the thalamus (410 pg), followed, in order, by the hypothalamus, medulla oblongata, telencephalon, and cerebellum. In ovine brain tissues, the highest concentration of KP (116 pg) was observed in the diencephalon, and the amount of KP in other tissues ranged between 20 and 40 pg. On the other hand, the concentration of GnIH in ovine brain was highest in the diencephalon (155 pg), followed, in order, by the midbrain, pons, and medulla oblongata, with GnIH concentration in other brain tissues being <60 pg.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.