Intravenous infusion of kisspeptin increased serum luteinizing hormone acutely and decreased serum follicle stimulating hormone chronically in prepubertal bull calves.
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abstract
Kisspeptin (KP) is a hypothalamic neuropeptide that stimulates the secretion of gonadotropin releasing hormone. To determine the acute and chronic effects of KP on serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH), prepubertal bull calves [121 (SD) weeks of age; 96.514.5kg BW] were administered one of four treatments [0.0 (control; CON), 0.125 (L-KP), 0.25 (M-KP), or 0.5 (H-KP) g of KP/kg BW/hour] by intravenous infusion for 76h. Blood samples were collected every 15min for the first (acute; 1-6h; Day 1) and last (chronic; 71-76h; Day 4) 6h of the intravenous infusions. Serum concentrations of LH and FSH were determined by radioimmunoassay. For each day, effects of treatment, time, and interactions on LH and FSH concentrations and pulse parameters were analyzed using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was a treatment effect (P=0.002) and a treatmenttime interaction during Day 1 (P=0.02) such that LH concentrations were greatest following administration of all doses of KP when compared to CON. However, there was no treatment effect (P=0.57) or a treatmenttime interaction during Day 4 (P=0.20) on serum LH concentrations. There was a treatment by day interaction (P=0.02) on mean serum FSH concentrations. Most notably, on Day 4 mean serum FSH concentrations during intravenous infusion of M-KP and H-KP doses were less than that of CON. There was a treatment by day interaction (P=0.0054) on FSH pulse amplitude concentrations, such that intravenous infusion of all doses of KP on Day 4 decreased FSH pulse amplitudes. In conclusion, acute infusion of KP increased LH concentrations and chronic infusion of KP decreased FSH concentrations. Despite the potential suppression of the hypothalamic-pituitary-gonadal axis with chronic infusion of KP, there are likely applications of KP, KP analogs, or KP receptor agonists to hasten the onset of puberty in livestock.
