<abstract xmlns="http://www.w3.org/1999/xhtml"><p> The influence of leptin on orexin A and the interaction of leptin with ghrelin in regulating the gonadotropic and somatotropic axes in seasonally polyestrous animals are not well understood. This study examined the effects of these factors as well as the mediating roles of specific ovine leptin antagonist (SOLA; mutant D23L/L39A/D40A/F41A) and photoperiod on luteinizing hormone (LH) and growth hormone (GH) secretion. Twenty-four ovariectomized, estradiol-implanted ewes were used in a replicated switchback design. The ewes were assigned randomly to 1 of 6 treatments (infused into the third ventricle 3 times at 0 (dusk), 1, and 2 h) as follows: control, Ringer-Locke buffer; leptin, 0.5 μg/kg b.w.; orexin A, 0.3 μg/kg b.w.; ghrelin, 2.5 μg/kg b.w.; SOLA, 50 μg/kg b.w. + orexin A, 0.3 μg/kg b.w.; and SOLA, 50 μg/kg b.w. + ghrelin, 2.5 μg/kg b.w. Blood samples (5 ml) were collected at 15-min intervals for 4 h. SOLA + orexin A resulted in an increase (P&lt;0.01) in the LH plasma concentration during short-day (SD) and long-day (LD) photoperiods. However, ghrelin and SOLA + ghrelin had the opposite effect. SOLA + orexin A resulted in an increase (P&lt;0.001) in the GH concentration compared with leptin or orexin A during the LD season. Ghrelin and SOLA + ghrelin increased the GH concentration (P&lt;0.01) regardless of the season. In summary, LH and GH secretion are seasonally dependent on relationships that are subject to photoperiodic regulation, and leptin is an important regulator of the effects of ghrelin and orexin A on the activities of the gonadotropic and somatotropic axes in sheep.</p></abstract>

The influence of leptin on orexin A and the interaction of leptin with ghrelin in regulating the gonadotropic and somatotropic axes in seasonally polyestrous animals are not well understood. This study examined the effects of these factors as well as the mediating roles of specific ovine leptin antagonist (SOLA; mutant D23L/L39A/D40A/F41A) and photoperiod on luteinizing hormone (LH) and growth hormone (GH) secretion. Twenty-four ovariectomized, estradiol-implanted ewes were used in a replicated switchback design. The ewes were assigned randomly to 1 of 6 treatments (infused into the third ventricle 3 times at 0 (dusk), 1, and 2 h) as follows: control, Ringer-Locke buffer; leptin, 0.5 μg/kg b.w.; orexin A, 0.3 μg/kg b.w.; ghrelin, 2.5 μg/kg b.w.; SOLA, 50 μg/kg b.w. + orexin A, 0.3 μg/kg b.w.; and SOLA, 50 μg/kg b.w. + ghrelin, 2.5 μg/kg b.w. Blood samples (5 ml) were collected at 15-min intervals for 4 h. SOLA + orexin A resulted in an increase (P<0.01) in the LH plasma concentration during short-day (SD) and long-day (LD) photoperiods. However, ghrelin and SOLA + ghrelin had the opposite effect. SOLA + orexin A resulted in an increase (P<0.001) in the GH concentration compared with leptin or orexin A during the LD season. Ghrelin and SOLA + ghrelin increased the GH concentration (P<0.01) regardless of the season. In summary, LH and GH secretion are seasonally dependent on relationships that are subject to photoperiodic regulation, and leptin is an important regulator of the effects of ghrelin and orexin A on the activities of the gonadotropic and somatotropic axes in sheep.

Induction of the Secretion of LH and GH by Orexin A and Ghrelin is Controlled in Vivo by Leptin and Photoperiod in Sheep

Annals of Animal Science

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

The influence of leptin on orexin A and the interaction of leptin with ghrelin in regulating the gonadotropic and somatotropic axes in seasonally polyestrous...

Induction of the Secretion of LH and GH by Orexin A and Ghrelin is Controlled in Vivo by Leptin and Photoperiod in Sheep

Article Category: The biology, physiology, reproduction, and health

Published Online: Feb 08, 2017

Page range: 155 - 168

Received: Feb 22, 2016

Accepted: Jun 02, 2016

DOI: https://doi.org/10.1515/aoas-2016-0041

Keywords
leptin antagonist, orexigenic hormones, luteinizing hormone, growth hormone, sheep

© by Dorota A. Zięba

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Induction of the Secretion of LH and GH by Orexin A and Ghrelin is Controlled in Vivo by Leptin and Photoperiod in Sheep

Article Category: The biology, physiology, reproduction, and health

Published Online: Feb 08, 2017

Page range: 155 - 168

Received: Feb 22, 2016

Accepted: Jun 02, 2016

DOI: https://doi.org/10.1515/aoas-2016-0041

Keywordsleptin antagonist, orexigenic hormones, luteinizing hormone, growth hormone, sheep

© by Dorota A. Zięba

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Keywords
leptin antagonist, orexigenic hormones, luteinizing hormone, growth hormone, sheep