In:
Acta Endocrinologica, Oxford University Press (OUP), Vol. 78, No. 2 ( 1975-02), p. 276-288
Abstract:
Neck-uptake studies, thyroid scintiscans and triiodothyronine (T 3 )- and thyroxine (T 4 )-kinetic studies were performed in normal rabbits and in animals producing antibodies against thyroid hormones. In immunized animals the radioiodide uptake and turnover were increased 3-fold and 6–17-fold, respectively. The thyroid glands were found to be enlarged scintigraphically and showed a denser tracer distribution pattern. T 3 and T 4 kinetic data were obtained from 5 rabbits immunized with T 3 (ABT 3 ), 4 immunized with T 4 (ABT 4 ) and from 5 controls. In T 3 immunized animals total T 3 in the serum rose from 86 to 59 000 ng/100 ml, in T 4 immunized rabbits total T 4 increased from 2.5 to 53.8 μg/100 ml. The fundamental principles of regulation were similar in both T 3 and T 4 immunized rabbits: There were enormous decreases in the total distribution spaces (TDS) as well as in the fractional turnover rates (k), resulting in markedly decreased metabolic clearance rates (MCR). The fall in T 3 -MCR was directly proportional to the T 3 binding activity of the sera. However, striking differences between the respective alterations of T 3 and T 4 kinetic data were obtained in the immunized animals: T 3 -MCR fell about 70-fold in ABT 3 , whereas T 4 -MCR was diminished 15-fold in T 4 immunized rabbits. In both groups of immunized animals T 3 -TDS decreased more than the T 3 fractional turnover, whereas T 4 -TDS was less affected than k T 4 . The T 3 production rates (PR) were increased 10-fold in ABT 3 and 5-fold in ABT 4 , whereas the increases in T 4 -PR were of only moderate degree both in ABT 3 and ABT 4 . Using presently available radiochemical methods the metabolic status of immunized rabbits could not be definitely assessed: "clinically" the animals were euthyroid. However, the dialyzable fraction in the serum of both T 3 and T 4 did not decrease proportionately to the enormous increase in total hormone concentration, so the free hormone concentrations were elevated over the normal. The results of the calculations of the cellular hormonal T 3 - and T 4 -clearance were more consistent with a euthyroid state: In ABT 4 the cellular metabolism of both hormones was not different from the normal; in ABT 3 a 1.7-fold increase in the cellular clearance of T 3 was accompanied by a significant decrease of that in T 4 .
Type of Medium:
Online Resource
ISSN:
0804-4643
,
1479-683X
DOI:
10.1530/acta.0.0780276
Language:
Unknown
Publisher:
Oxford University Press (OUP)
Publication Date:
1975
detail.hit.zdb_id:
1485160-X
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