Abstract

The diabetic C57BL/KsJ-db m mouse has abnormal thyroid hormone levels and indications of thyroid hormone resistance. To investigate the basis of these abnormalities, the hepatic nuclear thyroid hormone receptor was extracted with 0.4 M KCl, 1.1 mM MgCl2, 20 mM Tris/HCl, pH 7.9 from hepatocyte nuclei of normal C57BL/KsJ, heterozygous C57BL/KsJ-db m (db/m), and diabetic C57BL/KsJ-db m (db/db) mice. Normal and heterozygous mice were grouped together as the controls. Triiodothyronine (T3) binding studies at 4°C using nitrocellulose filtration to separate free T3 from receptor bound T3 demonstrated an apparent dissociation constant of (1.3 ± 0.8) x 10-10 M for controls which was significantly less than that of (8.7 ± 10.4) x 10-10 M for diabetic mice (p < 0.01, one tailed t-test). However, the maximum binding capacity were not significantly different at (4.6 ± 3.3) x 10-13 moles/mg DNA for controls and (3.2 ± 4.6) x 10-13 moles/mg DNA for diabetic mice. Triiodothyronine-receptor dissociation rates also demonstrated a significantly greater dissociation of the diabetic T3-receptor complex (p < 0.05, one-tailed t-test). The half-life for dissociation was 101 ± 22 hours for controls versus 70 ± 21 hours for diabetics. Although equilibrium binding conditions were not achieved, the use of Scatchard analysis to compare the controls and diabetics is justified by the similar conclusion from dissociation experiments that T3 binding is significantly decreased in the diabetic mouse. Triiodothyronine was found to interact freely with the receptor, binding 98 ± 2% of that predicted to be bound if T3 were free in solution, even though 70 ± 2% of the T3 is initially adsorbed to the glassware. However, adsorption to glassware did explain the negative values for specific binding above 10-6 M T3 as calculated from the difference between total and nonspecific binding. Isoelectric focusing and sedimentation velocity of the receptor preparation did not demonstrate any differences between control and diabetic mice. Comparison of the level of saturation of the nuclear T3 receptor in the diabetic mouse to other obese syndromes suggests that the decreased T3 binding reported here has a significant impact on the obesity of the diabetic mouse.

LLU Discipline

Biochemistry

Department

Biochemistry

School

Graduate School

First Advisor

George M. Lessard

Second Advisor

R. Bruce Wilcox

Third Advisor

E. Clifford Herrmann

Fourth Advisor

Lamont Murdoch

Fifth Advisor

Richard Fehn

Sixth Advisor

Terry D. Shultz

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

1988

Date (Title Page)

6-1988

Language

English

Library of Congress/MESH Subject Headings

Triiodothyronine; Receptors, Thyroid Hormone; Binding Sites; Thyroid Hormones

Type

Dissertation

Page Count

xii; 148

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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