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Influence of short‐term oestradiol treatment on plasma thyroid hormone kinetics in rainbow trout, Salmo gairdneri
Author(s) -
Cyr D. G.,
Eales J. G.
Publication year - 1990
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1990.tb05619.x
Subject(s) - medicine , endocrinology , trout , rainbow trout , thyronine , hormone , thyroid , biology , salmo , chemistry , thyroid hormones , fish <actinopterygii> , fishery
The effects of 17β‐oestradiol (E 2 ) on plasma kinetics of thyroid hormones (T 4 , l‐thyroxine; T 3 , 3,5,3′‐triiodo‐l‐thyronine) were studied in immature rainbow trout. E 2 ‐3‐benzoate (0.5 mg/100 g) was injected intraperitoneally on days 0 and 3, and on the morning of day 4 each trout received an intracardiac injection of either [ 125 I]T 4 and Na 131 I or [ I25 I]T 3 . Groups of trout were bled and killed from 5 min to 4 days post‐injection of tracer. E 2 did not alter the plasma T 4 level but depressed the T 4 plasma clearance rate, plasma‐to‐total tissue flux of T 4 and thyroidal T 4 secretion rate. Monodeiodination of T 4 to T 3 was also depressed, as judged from plasma [ I25 I]T 3 and I25 I − levels in [ 125 I]T 4 ‐injected trout. E 2 had no major effect on T 3 plasma clearance rate but depressed the plasma T 3 level, plasma‐to‐total tissue flux of T 3 and the T 3 plasma appearance rate. E 2 had no influence on biliary transport of [ I25 I]T 4 or [ 125 I]T 3 . The above results suggest that E 2 , at the dose range employed, depresses extrathyroidal T 4 to T 3 conversion, which may in turn decrease plasma T 4 clearance and thyroidal T 4 secretion.