[Effects of testosterone and growth hormone on plasma concentrations of orexin in diet restricted rams]

ABSTRACT

It has been established that multiple neuroendocrine factors such as orexin operate as metabolic signals for the reproductive tract. Since the effects of testosterone and growth hormone on concentration of orexin in rams have not been studied, the goal of this study was to determine the effect of testosterone and growth hormone on mean plasma concentrations of orexin in rams fed restricted diets. Rams were randomly divided into 2 groups. Animals in first group were fed 100% of their required daily food and those in the second group were fed 50% of food fed to the first group for 10 days. Consequently, the rams in all groups received 6microg /Kg BW testosterone on days 7 and 8 and 6microg /Kg BW Testosterone and 5 microg /Kg BW growth hormone on days 9 and 10 of the experiment. Blood samples were collected from the jugular veins at -120 and +120 minutes of infusions. for orexin assay, Plasma orexin were measured by a homologous double-antibody radioimmunoassay [RIA]. Injection of different dosages of testosterone and combination of testosterone and growth hormone in the 50%-diet, significantly [P<0.05*] increased the mean plasma concentrations of orexin, while in the 100%-diet this had no effect. Results indicate that testosterone and growth hormone may increase mean concentrations of orexin in animals fed lower than their daily food requirement