Effects of short term genotropin (rgGH) subcutaneous injection on active ghrelin concentration in rat plasma, stomach, kidney & pancreas. (c2007)

Abstract

Ghrelin is a 28-amino acid octanoylated peptide that has been isolated from rat stomach and stimulates pituitary growth hormone secretion. Growth hormone (GH) is a potent endocrine modulator of growth and metabolism. Genotropin is a recombinant human growth hormone (rhGH) that increases lean body mass, skeletal muscle mass, muscle force and strength, aerobic performance, and fat loss. A very important issue regarding ghrelin physiology is whether an axis or loop exists between pituitary GH on one hand and plasma, stomach, pancreas and kidney ghrelin on the other hand thus reflecting how GH elevations or reductions directly affect ghrelin homeostasis and secretion. The purpose of this experiment was to study the effects of a 5 day treatment of genotropin subcutaneous injection (2, 20, and 100 μg/rat/day) on active ghrelin concentration in rat plasma, stomach, kidney, and pancreas samples.. The Active Ghrelin ELISA kit results showed a significant increase in active ghrelin concentration in the rat plasma samples and a significant decrease in active ghrelin concentration in the rat stomach, kidney, and pancreas supernatants. Moreover, protein results using Lowry assay for protein determination showed that genotropin injection led to an increase in protein concentration in stomach and kidney samples and to a drastic decrease in protein concentration in the pancreas samples. Calculations revealed that genotropin injection decreased active ghrelin concentration per μg of protein in stomach and kidney supernatant but had no significant effect on active ghrelin concentration per μg of protein in pancreas supernatant. In conclusion, these findings show that GH lowers active ghrelin concentration in the stomach, kidney, and pancreas samples thus suggesting a feedback loop between stomach, kidney and pancreas ghrelin on one hand, and pituitary GH on the other hand.