In vitro evidence that leptin suppresses melatonin secretion during long days and stimulates its secretion during short days in seasonal breeding ewes

Zieba, Dorota A.; Klocek, Beata; Williams, Gary L.; Romanowicz, Katarzyna; Boliglowa, Lukasz; Wozniak, Malgorzata

doi:10.1016/j.domaniend.2006.06.004

« PreviousDomestic Animal Endocrinology
Volume 33, Issue 3 , Pages 358-365, October 2007

In vitro evidence that leptin suppresses melatonin secretion during long days and stimulates its secretion during short days in seasonal breeding ewes

Dorota A. Zieba
- Department of Sheep and Goat Breeding, University of Agriculture, Krakow 30-059, Poland
- Corresponding author. Tel.: +48 12 662 40 89; fax: +48 12 633 33 07.
Beata Klocek
- Department of Sheep and Goat Breeding, University of Agriculture, Krakow 30-059, Poland
Gary L. Williams
- Animal Reproduction Laboratory, Texas A&M University Agricultural Research Station, Beeville, TX 78102, USA
Katarzyna Romanowicz
- Institute of Animal Physiology and Nutrition, Department of Endocrinology, Polish Academy of Sciences, Jablonna, Poland
Lukasz Boliglowa
- Department of Sheep and Goat Breeding, University of Agriculture, Krakow 30-059, Poland
Malgorzata Wozniak
- Department of Sheep and Goat Breeding, University of Agriculture, Krakow 30-059, Poland

Received 28 February 2006; received in revised form 19 June 2006; accepted 19 June 2006. published online 25 July 2006.

Abstract

Recent observations in seasonal-breeding mammals indicate that the hypothalamus is programmed to become leptin resistant during long days (LD) and leptin sensitive during short days (SD). These observations support the possibility that photoperiod mediates at least part of its effects on melatonin secretion through changes in leptin sensitivity. Herein we examined the interaction of season and recombinant ovine leptin (oleptin) on melatonin secretion by pineal explants in short-term culture. Glands were collected after sunset from eight ewes during LD (March, April, May, June) and from an additional eight ewes during SD (September, October, November, December). Glands were transected saggitally and coronally into quarters, with each equilibrated in 2.5ml of DMEM for 120min, followed by a 3h incubation in medium containing either 0 or 50ng/ml of oleptin. Treatment with oleptin reduced (P<0.001) melatonin secretion compared to controls during LD by approximately 22% at 2, 2.5 and 3h of culture. However, in cultures from glands collected during SD, oleptin stimulated (P<0.078) melatonin secretion approximately 50% compared to control. These effects were consistent throughout each respective season. We conclude that the secretion of melatonin from the ovine pineal gland is negatively responsive to leptin during LD, whereas leptin may stimulate melatonin secretion during SD.