Peptide

Human kisspeptin-54 was synthesised by Advanced Biotechnology Centre (Imperial College London, London, UK) and further purified and tested as previously described [28] consistent with the standards for physiological research studies. Vials of freeze-dried kisspeptin-54 were stored at −20°C and then reconstituted with 0.9% saline. The rate of infusion was calculated based on body weight. A fixed volume of the peptide solution from the reconstituted vial was transferred into a 50-mL syringe containing Gelofusine (5% vol/vol) (B. Braun Medical, Sheffield, UK), which was used as the vehicle to minimise peptide absorption to the administration apparatus [31].

Gonadorelin 100 µg (GnRH) was purchased from Intrapharm laboratories Ltd. (Maidenhead, UK). It was reconstituted with the supplied sterile solvent, which contained 2% benzyl alcohol and water for injection. A fixed volume of peptide solution was then transferred into a 50-mL syringe containing Gelofusine and infused at a rate determined by the weight-based calculation.