Investigation of the biological activity of Caspian kutum kisspeptin after adding an acetyl group to Tyr1

In the present study, the goldfish kisspeptin peptide was synthesized using the solid phase synthesis method according to the nucleotide sequence of the goldfish (Carassius auratus) kiss1 gene. Next, an acetyl group was added to the amino group of Tyr1 to increase the biological activity. The synthesized peptide (referred to as ACKiss1) was purified by RP-HPLC and its structure was confirmed using electrospray ionization (ESI) mass spectrometry. To determine the biological activity, ACKiss1, native Kiss1 and commercial GnRH hormone were injected to goldfish, some important parameters of the reproductive physiology were studied. Kiss1 and ACKiss1 were injected with a dosage of 100 μg/kg fish body weight and GnRH was injected with dosages of 100 and 200 μg/kg body weight. 6 hours after injection, blood was taken from the caudal vein and sex hormones were measured in plasma. 24 hours after injection, reproductive indices were measured in a series of fish. In another series of fish, 24 hours after injection, ovarian and brain tissues were separated for histological studies and expression of the reproductive-related genes (cyp19b, gpr54a, and kiss1). The results revealed that significant changes in biochemical parameters and gene expression were recorded in both brain tissue samples and ovarian tissue in ACKISS1 treatment. It was also found in ovarian histology that under the influence of kisspeptin and GnRH, the number of mature oocytes increased significantly.