Stress-Induced Changes in Tyrosine Hyroxylase Enzyme Activity and Adrenomedullin Levels in Rat Hypothalamus, Adrenal Medulla and Heart Tissues

In this study, it was aimed to investigate the effects of chronic cold stress on adrenomedullin levels and tyrosine hydroxylase enzyme activities in some rat tissues. In this study, 12 female Sprague Dawley rats weighing 200 to 250 g were used. Rats were housed under diurnal lighting conditions (12-12 h) with free access to food and water. For this study, rats were divided into two groups, namely control group and cold stress treated group. Adrenomedullin levels were measured by high performance liquid chromatography. Tyrosine hydroxylase enzyme activities was spectrometrically measured. Tyrosine hydroxylase activity was found to be increased significantly (p<0.05) in adrenal medulla, hypothalamus and heart tissues depending on cold stress treatment. Adrenomedullin levels were determined to be decreased in the cold stress treatment group. The differences of between control and cold stress treatment groups were significant (p<0.05). The results suggested that adrenomedullin may play a possible role in adaptation to stress. Exposure to cold increases the synthesis and release of catecholamines. Tyrosine hydroxylase is the rate limiting step in the biosynthesis of catecholamines for this reason cold stress increased tyrosine hyroxylase enzyme activities. Further studies are needed to reveal correlation between adrenomedullin, tyrosine hydroxylase and cold stress.