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Urinary excretion of thyroid hormones in rainbow trout, Oncorhynchus mykiss.

Abstract：

:Urinary excretion of the thyroid hormones (TH) L-thyroxine (T4), and 3,5,3'-triiodo-L-thyronine (T3) and their derivatives was studied in urinary-catheterized rainbow trout (mean wt. 227 g) fasted for 2 days under a 12-hr L:12-hr D photocycle in running water (12 degrees). Catheterized trout were intracardiac-injected with [125I]T4 (*T4) or [125I]T3 (*T3) and urine was collected as 2-hr fractions over 48 hr. The 125I corresponding to I-, TH conjugates (sulfates and glucuronides), or TH was separated by LH-20 column chromatography and HPLC. Urine production (daily mean, 72.5 ml/kg/day) was lowest during the scotophase and doubled at the start of photophase, causing acute fluctuations in excretion of 125I-labeled materials, and implying dependence on glomerular filtration rate. During the first 48 hr, 8.2% of *T4 (I-, 3.6%: TH conjugates, 1.7%; TH, 2.9%) and 6.7% of injected *T3 (I-, 1.8%; TH conjugates, 2.5%; TH, 2.4%) was excreted in urine; 32.6% (*T4) and 26.4% (*T3) was in the gall bladder; 45.5% (*T4) and 45.7% (*T3) were in the remaining carcass; and 13.7% (*T4) and 23.7% (*T3) were lost via other routes. We extrapolate that about 15% of *T4-injected and 12% of *T3-injected total radioactivity would be excreted ultimately in urine, with 8.4% (*T4) and 9.0% (*T3) as TH or their conjugates. Neither a T4 nor a T3 challenge (20 ng/g) influenced the amount of radioactive loss in urine over 48 hr. We conclude that the urine is a significant route for excretion of TH and their conjugates, and that urinary TH loss depends to a large extent on the rate of urine production.

journal_name

Gen Comp Endocrinol

journal_title

General and comparative endocrinology

authors

Parry JE,Zhang C,Eales JG

doi

10.1006/gcen.1994.1128

subject

Has Abstract

pub_date

1994-08-01 00:00:00

pages

310-9

issue

2

eissn

0016-6480

issn

1095-6840

pii

S0016-6480(84)71128-2

journal_volume

95

pub_type

杂志文章

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