The effects of cold exposure and cold plus phenoxybenzamine treatment on tyrosine hydroxylase (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. | Tr. J. of Biology 22 (1998) 197-203 © TÜBİTAK The Effects of Phenoxybenzamine and Cold Stress On Tyrosine Hydroxylase Enzyme Activity and Expression of Tyrosine Hydroxylase Gene in the Rat Adrenal Medulla Muhittin YÜREKLİ İnönü University Arts and Science Faculty Molecular Biology Department Malatya-TURKEY Received: Abstract: The effects of cold exposure and cold plus phenoxybenzamine treatment on tyrosine hydroxylase (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 intraperitoneally () at 20 mg/kg, which was prepared in 5% ethanol containing % NaCL 3 3 TH activity was measured by monitoring the formation of H2O as a product of L-( H)-tyrosine 3 3 hydroxylation, the formation of L-( H)-dopa from L-( 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<). Key Words: Cold exposure, adrenal medulla, phenoxybenzamine, tyrosine hydroxylase tyrosine hydroxylase mRNA Phenoxybenzamine ve Soğuk Stresinin Sıçan Adrenal Medulla Tirozin Hidroksilaz Enzim Aktivitesi ve Tirozin Hidroksilaz Gen İfadesi Üzerine Etkileri Özet: Soğuk uygulaması ve soğuğa ek olarak phenoxybenzamine uygulamasının, tirozin hidroksilaz (TH) ve TH mRNA seviyesi üzerindeki etkileri Sprague Dawley (SD) sıçanlarının adrenal medullasında araştırıldı. SD sıçanları 48 saat 4 °C’de soğuğa maruz bırakıldı. Phenoxybenzamine uygulaması % NaCl içeren % 5 etanol içinde hazırlanarak 20 mg/kg olacak şekilde periton içine () yapıldı. TH aktivitesi, L-(3 H)-tirozinden L-(3 H)-dopa oluşurken, L-(3 .
