Isolation and characterization of ovine tyrosine hydroxylase mRNA.

Tyrosine hydroxylase (TH) cDNA has been characterized in rodents and primates, but only a few studies have been developed in ungulates, except in cows. Because sheep is a species used for many physiological studies, it was of interest to clone TH cDNA in this species. Ovine TH cDNA was purified from a library of sheep adrenal glands. The entire cDNA was 1,721 bp long. It presented a higher percentage of similarity with bovine TH cDNA (93%) than with rodent cDNAs (75%). The deduced amino acid sequence was 490 amino acids long and had 96% similarity with the 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 35S-dATP to detect TH mRNA by in situ hybridization. Strong labelings were observed on adrenal medulla and on noradrenergic and dopaminergic neurons in the sheep but also in the cow and pig. This labeling matched completely TH immunohistochemical staining obtained on the same sections with anti-TH antibodies. Ovine TH cDNA is a useful tool to study the variations of TH mRNA levels in sheep catecholaminergic neurons.