Influence of castration and testosterone replacement on hypothalamic tyrosine hydroxylase activity in the rat
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Hypothalamic tyrosine hydroxylase (TH) activity of castrate rats is modulated by testosterone propionate (TP) in vivo. Kinetic studies revealed that bothVmax andKm were virtually unaltered for substrate tyrosine in the presence of an excess of DMPH4 cofactor. TP replacement to castrate rats increased theKm for added DMPH4 cofactor, whileVmax decreased. These results suggest that TP decreases TH activity of castrate rats by inhibiting the enzymereduced pteridine cofactor complex.
KeywordsTyrosine Propionate Testosterone Kinetic Study Tyrosine Hydroxylase
- 5.R. A. Müller, H. Thoenen andJ. Axelrod, J. Pharmac. exp. Ther.169, 74 (1969).Google Scholar
- 7.T. P. Waalkes andS. Udenfriend, J. Lab. clin. Med.50, 733 (1972).Google Scholar
- 9.E. G. McGeer, S. Gibson, J. A. Wader andP. L. McGeer, Can. J. biochem.45, 1942 (1967).Google Scholar
- 10.K. E. Moore andJ. A. Dominic, Fedn. Proc.30, 859 (1971).Google Scholar