, Volume 32, Issue 8, pp 1076–1077 | Cite as

Influence of castration and testosterone replacement on hypothalamic tyrosine hydroxylase activity in the rat

  • C. W. Beattie
  • Margaret M. Martin
Specialia Endocrinologica


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.


Tyrosine Propionate Testosterone Kinetic Study Tyrosine Hydroxylase 


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Copyright information

© Birkhäuser-Verlag 1976

Authors and Affiliations

  • C. W. Beattie
    • 1
  • Margaret M. Martin
    • 1
  1. 1.Endocrinology SectionWyeth Laboratories, Research DivisionPhiladelphiaUSA

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