Expression of inhibitory G proteins in adenomatous thyroid glands obtained from hyperthyroid cats

Cynthia R. Ward Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104-6010.
Present address is the Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA 30602.

Search for other papers by Cynthia R. Ward in
Current site
Google Scholar
PubMed
Close
 VMD, PhD
,
Sara E. Achenbach Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104-6010.

Search for other papers by Sara E. Achenbach in
Current site
Google Scholar
PubMed
Close
 BA
,
Mark E. Peterson Caspary Research Institute, Animal Medical Center, 510 E 62nd St, New York, NY 10021.

Search for other papers by Mark E. Peterson in
Current site
Google Scholar
PubMed
Close
 DVM
,
Kenneth J. Drobatz Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104-6010.

Search for other papers by Kenneth J. Drobatz in
Current site
Google Scholar
PubMed
Close
 DVM
, and
David Holt Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104-6010.

Search for other papers by David Holt in
Current site
Google Scholar
PubMed
Close
 BVSc

Abstract

Objective—To identify within guanosine triphosphate–binding proteins (G proteins) the subset of inhibitory G proteins (Gi) that have decreased expression in adenomatous thyroid glands obtained from hyperthyroid cats.

Sample Population—Adenomatous thyroid glands obtained from 5 hyperthyroid cats and normal thyroid glands obtained from 3 age-matched euthyroid cats.

Procedure—Expression of Gi1, Gi2, and Gi3 in enriched membrane preparations from thyroid glands was quantified by use of immunoblotting with Gi subtype-specific antibodies.

Results—Expression of Gi2 was significantly decreased in tissues of hyperthyroid glands, compared with expression in normal thyroid tissue. Expression of Gi1 and Gi3 was not significantly different between normal thyroid tissues and tissues from hyperthyroid glands.

Conclusions and Clinical Relevance—A decrease in Gi2 expression decreases inhibition of adenylyl cyclase and allows a relative increase in stimulatory G protein expression. This results in increased amounts of cAMP and subsequent unregulated mitogenesis and hormone production in hyperthyroid cells. Decreased Gi2 expression may explain excessive growth and function of the thyroid gland in cats with hyperthyroidism. (Am J Vet Res 2005;66:1478–1482)

Abstract

Objective—To identify within guanosine triphosphate–binding proteins (G proteins) the subset of inhibitory G proteins (Gi) that have decreased expression in adenomatous thyroid glands obtained from hyperthyroid cats.

Sample Population—Adenomatous thyroid glands obtained from 5 hyperthyroid cats and normal thyroid glands obtained from 3 age-matched euthyroid cats.

Procedure—Expression of Gi1, Gi2, and Gi3 in enriched membrane preparations from thyroid glands was quantified by use of immunoblotting with Gi subtype-specific antibodies.

Results—Expression of Gi2 was significantly decreased in tissues of hyperthyroid glands, compared with expression in normal thyroid tissue. Expression of Gi1 and Gi3 was not significantly different between normal thyroid tissues and tissues from hyperthyroid glands.

Conclusions and Clinical Relevance—A decrease in Gi2 expression decreases inhibition of adenylyl cyclase and allows a relative increase in stimulatory G protein expression. This results in increased amounts of cAMP and subsequent unregulated mitogenesis and hormone production in hyperthyroid cells. Decreased Gi2 expression may explain excessive growth and function of the thyroid gland in cats with hyperthyroidism. (Am J Vet Res 2005;66:1478–1482)

All Time Past Year Past 30 Days
Abstract Views 20 0 0
Full Text Views 1033 924 225
PDF Downloads 94 58 9
Advertisement