Radiothyroxine metabolism in several freshwater teleost fishes

• Published in: Canadian Journal of Zoology
• Main Author: Eales, J. G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1972
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Burbot
• Online Access: http://dx.doi.org/10.1139/z72-086; http://www.nrcresearchpress.com/doi/pdf/10.1139/z72-086

The metabolism of intraperitoneally injected radiothyroxine labeled with 125 I in 3′ and 5′ positions (*T 4 ) was followed in several starved freshwater teleosts acclimated at 12–13 °C.Biological half-lives for initial loss of plasma PB 125 I (*T 4 ) were 7.9 h (goldfish), 8.7 h (rainbow trout), 12.2–28.5 h (channel catfish), 19.2 h (sucker), 24.0–37.6 h (burbot), and 56.6–138.0 h (brown bullhead). Frequently, a single exponential decrease in plasma PB 125 I did not occur, and the usually large *T 4 distribution spaces suggested that injected *T 4 might not rapidly enter the circulation from the injection site. Plasma radioactive derivatives included 3,5,3′ triiodo-L-thyronine.Biliary *T 4 excretion varied considerably between species and could relate to feeding habits.