[ effect of L-tryptophan on growth hormone and thyroid hormones secretion in growing lambs]

ABSTRACT

Survey on effects of serotonin agonist on the plasma concentrations of growth hormone [GH] and thyroid hormones [T[3] and T[4]; TH]. Repeated measures [GLM] were used. Twenty Kurdish lambs 3-4 months old. Animals were randomly divided into four groups. The first group [control] received 2 ml normal saline. The second, third and fourth groups received 120, 240 and 480 mg/kg body weight L-tryptophan through jugular vein, respectively. blood samples were collected in three periods including before [days 1, 4, 5 and 6], during [days 7, 8, 9, 10, 11, 12, 13, 14, 15, 18, 22, 26, 30 and 34] and after [days 36, 37 and 38] injections. Plasma concentrations of these hormones in unextracted samples were analyzed by radioimmunoassay kit [Tabeshyarnoor kits company, Tehran, Iran]. Injection of serotonin agonist increased mean plasma concentration [MPC] of GH [P<0.01]. There are no significant differences in MPC of GH within the treated groups. Effects of blood sampling times, period [before, during, after injection] and their interaction with treatment on MPC of GH were significant[ P<0.01]. MPC of TH [T[3] and T[4]] in all of the treated groups was significantly increased compare with control one [P<0.01]. There are no significant differences in MPC of TH within the treated groups. Effects of blood sampling times and period [before, during and after injection] and also their interactive effects with treatment were significant. According to statistical analysis of data we can suggest that serotonin agonist stimulates GH and TH secretion simultaneously