THIRD VENTRICLE GHRELIN INFUSION EFFECT ON THE METABOLIC PARAMETERS UNDER DIFFERENT ENERGY LEVELS IN DIETS

The goal of this study was to determine whether ghrelin affects the mean plasma concentrations of metabolic parameters such as thyroxine (T4), triiodothyronine (T3), growth hormone (GH), insulin, glucagon, glucose, fatty acid and urea in the goats fed different energy content in diets. Sixteen goats were randomly divided into 4 groups. Animals in groups 1 and 2 were fed 100 % and animals in groups 3 and 4 were fed a 50 % energy content in their diet for 20 days. After 20 days, animals in groups 1 and 3 received a daily infusion of 1 ug ghrelin, while groups 2 and 4 received a daily infusion of 2 ug galanin into their third ventricle for 5 days. Blood samples were collected daily from the jugular veins before infusions on day 4 until 4 days after the last infusions of ghrelin. Samples were assayed for plasma T3, T4, GH, insulin and glucagon concentrations by double-antibody RIA. Glucose, fatty acid, and urea concentrations were also measured. Lower dietary energy intake and infusions of 1 and 2 ug ghrelin significantly (P < 0.01) decreased the mean plasma concentrations of T3, T4, insulin, and glucose, and significantly (P < 0.01) increased the mean plasma concentrations of GH, glucagon, fatty acid, and urea of the animals in groups 3 and 4. Different dosages of the ghrelin infusions did not change the plasma concentrations of the metabolic parameters in the animals fed a normal energy content in diets. The results of this experiment indicated that ghrelin may negatively affect the T3, T4, insulin, and glucose and increase GH, glucagon, fatty acid, and urea in the goats with a negative energy balance, but not in those with the positive energy balance.