Endocrine Abstracts

Ghrelin is a recently discovered endogenous ligand of the Growth Hormone (GH) secretagogue receptor, and is primarily produced by the stomach. Ghrelin acts on the hypothalamic-pituitary axis to stimulate GH release and may determine hepatic sensitivity of Insulin-like Growth Factor-I (IGF-I) to GH. Maternal chronic cold exposure by winter shearing has shown to increase lamb birth weight, however, the effects on Ghrelin are not yet known.

Twenty-six multiparous twin-bearing ewes of similar body weight were entered into the study, thirteen were shorn (S) during mid gestation and thirteen left unshorn (US). Six out of each group were then nutrient restricted (NR; fed 50% of total energy requirements) over the final month of gestation and seven controls (C) were fed to 100% of requirements until term. One lamb from each ewe was tissue sampled at 1 day of age. The relative abundance of IGF-I, GH receptor (R) and Ghrelin mRNA to an 18S rRNA standard were determined using RT-PCR. Results are given as means with their standard errors in arbitrary units (a.u.) and are expressed as a percentage of a reference sample present on all gels.

Maternal cold exposure resulted in significantly heavier total body weight at one day in SC as compared to the US group and increased abundance of Ghrelin mRNA (SC 184 plus/minus SD 16; USC 50 plus/minus SD 10 a.u. (P<0.05)). Nutrient restriction abolished this effect in conjunction with a smaller liver weight. There were no significant differences between IGF-I and GHR abundance between the groups. In conclusion, maternal cold exposure promotes fetal growth and hepatic expression of Ghrelin in the absence of any effect on the GH-IGF axis. These effects are dependent upon maternal nutrition.