Kisspeptin (KP) , a neuroendocrine regulator of reproduction,is hypothesized to be an integrator of metabolism and hormones critical to the regulation of reproduction. Lactation is associated with enhanced growth horm...Kisspeptin (KP) , a neuroendocrine regulator of reproduction,is hypothesized to be an integrator of metabolism and hormones critical to the regulation of reproduction. Lactation is associated with enhanced growth hormone (GH) responsiveness and reduced fertility. Our study was designed to determine the effects of lactation on KP-stimulated GH and luteinizing hormone (LH) secretion. Five non-lactating and five lactating dairy cows were used in the study. Experiments were conducted with lactating cows at weeks 1,5 and 11 after parturition. The experimental treatments (saline and KP [100 and 400 pmol / kg body weight]) were given intravenously and blood was collected and plasma was stored until later assay to determine concentrations of GH,LH,progesterone and nonesterified fatty acids. We found that neither dose of KP stimulated an increase in GH secretion. The low dose ofKP increased (P <0. 05) LH concentrations only in lactating cows. The higher dose of KP elicited an increase in circulating LH concentrations in both lactating and non-lactating cows. The lower dose of KP increased (P < 0. 05) the area under the curve for LH only in cows during week 5 of lactation,and the area under the curve of LH following the highest dose of KP was greater (P < 0. 05) in cows during week 5 of lactation than that for the other groups of cows. In summary,lactation status and stage of lactation did not change the sensitivity of the GH system to KP. However,an effect of stage of lactation on KP-stimulated LH secretion was detected in the dairy cows. Study of the KP system during lactation in dairy cows may provide critical insights into the mechanisms for lactation-associated changes in the reproductive axis.展开更多
基金an Animal Health and Disease Research grant from the College of Veterinary Medicine at Auburn University (Auburn,AL)supported by an Agricultural and Food Research Initiative Competitive grant no. 2010-6520620647 from the USDA National Institute of Food and Agriculture
文摘Kisspeptin (KP) , a neuroendocrine regulator of reproduction,is hypothesized to be an integrator of metabolism and hormones critical to the regulation of reproduction. Lactation is associated with enhanced growth hormone (GH) responsiveness and reduced fertility. Our study was designed to determine the effects of lactation on KP-stimulated GH and luteinizing hormone (LH) secretion. Five non-lactating and five lactating dairy cows were used in the study. Experiments were conducted with lactating cows at weeks 1,5 and 11 after parturition. The experimental treatments (saline and KP [100 and 400 pmol / kg body weight]) were given intravenously and blood was collected and plasma was stored until later assay to determine concentrations of GH,LH,progesterone and nonesterified fatty acids. We found that neither dose of KP stimulated an increase in GH secretion. The low dose ofKP increased (P <0. 05) LH concentrations only in lactating cows. The higher dose of KP elicited an increase in circulating LH concentrations in both lactating and non-lactating cows. The lower dose of KP increased (P < 0. 05) the area under the curve for LH only in cows during week 5 of lactation,and the area under the curve of LH following the highest dose of KP was greater (P < 0. 05) in cows during week 5 of lactation than that for the other groups of cows. In summary,lactation status and stage of lactation did not change the sensitivity of the GH system to KP. However,an effect of stage of lactation on KP-stimulated LH secretion was detected in the dairy cows. Study of the KP system during lactation in dairy cows may provide critical insights into the mechanisms for lactation-associated changes in the reproductive axis.
