Turkish Journal of Biology

Abstract: The effects of cold exposure and cold plus phenoxybenzamine treatment on tyrosine hydrox-ylase (TH) activity and TH m RNA levels were investigated in the adrenal medulla of Sprague Dawley (SD) rats. SD rats were exposed to cold (4 °C) for 48 hours. Phenoxybenzamine was injected intra-peritoneally (i.p) at 20 mg/kg, which was prepared in 5% ethanol containing 0.9 % NaCL TH activity was measured by monitoring the formation of 3 H 2 O as a product of L-(3 H)-tyrosine hydroxylation, the formation of L-(3 H)-dopa from L-(3 H)-tyrosine. Total adrenal RNA was isolated and blotted onto a nylon membrane and the immobilized RNA was then hybridized from TH cDNA probe. TH mRNA was assayed by densitometric scanning of the autoradiograms with a videodensitometer. TH activity and mRNA levels were found to be significantly increased in the adrenal medulla of SD rats exposed to cold for 48 hours and treated with cold plus phenoxybenzamine (P<0.01).

Key Words: Cold exposure, adrenal medulla, phenoxybenzamine, tyrosine hydroxylase tyrosine hydroxylase mRNA