ISOLATION AND CHARACTERIZATION OF OVINE TYROSINE-HYDROXYLASE MESSENGER-RNA

Tyrosine hydroxylase (TH) cDNA has been characterized in rodents and p rimates, but only a few studies have been developed in ungulates, exce pt in cows. Because sheep is a species used for many physiological stu dies, it was of interest to clone TH cDNA in this species. Ovine TH cD NA was purified from a library of sheep adrenal glands. The entire cDN A was 1,721 bp long, It presented a higher percentage of similarity wi th bovine TH cDNA (93%) than with rodent cDNAs (75%). The deduced amin o acid sequence was 490 amino acids long and had 96% similarity with t he bovine amino acid sequence. The entire cDNA and different fragments obtained with endonuclease restriction enzymes were cloned in plasmid pUC 18 and were labeled with S-35- dATP to detect TH mRNA by in situ hybridization. Strong labelings were observed on adrenal medulla and o n noradrenergic and dopaminergic neurons in the sheep but also in the cow and pig. This labeling matched completely TH immunohistochemical s taining obtained on the same sections with anti-TH antibodies. Ovine T H cDNA is a useful tool to study the variations of TH mRNA levels in s heep catecholaminergic neurons.