Growth hormone stimulates hepatic thyroxine 5′-monodeiodinase activity and 3,5,3′-triiodothyronine levels in rainbow trout (Salmo gairdneri)

Intraperitoneal injection of rainbow trout with 0.4 μg/g of human growth hormone increased plasma levels of 3,5,3′-triiodo-l-thyronine and Vmax of the hepatic microsomal 5′-monodeiodinase enzyme that converts thyroxine to T3, with no effect on Km or plasma T4 levels

Deborah L. MacLatchy; J.G. Eales

2005

Scholarcy highlights

  • Intraperitoneal injection of rainbow trout with 0.4 μg/g of human growth hormone increased plasma levels of 3,5,3′-triiodo-l-thyronine and Vmax of the hepatic microsomal 5′-monodeiodinase enzyme that converts thyroxine to T3, with no effect on Km or plasma T4 levels
  • A dose of 0.4 μg human growth hormone/g increased both plasma T3 and Vmax as early as 8 hr postinjection. Maximal levels for both parameters occurred at 24 hr pi and significant stimulation was sustained to 48 hr pi
  • In trout injected with hGH over a dose range of 0.1–1.0 μg/g and sampled at 24 hr pi, both Vmax and plasma T3 increased in a dose-dependent manner
  • It is concluded that the increase in the level of functional hepatic 5′D may contribute to the rapid hGH-induced elevation in plasma T3
  • It is concluded that the increase in the level of functional hepatic 5′-monodeiodinase enzyme may contribute to the rapid human growth hormone-induced elevation in plasma T3

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