Rat pancreatic nuclear thyroid hormone receptor: characterization and postnatal development.
To document the presence of 3,5,3'-triiodothyronine nuclear receptor in the rat pancreas, the solubilized pancreatic nuclear fraction was characterized for its binding to 3,5,3'-L-triiodothyronine. Binding was found to be reversible, saturable, and specific. Scatchard analysis revealed a single class of 3,5,3'-L-triiodothyronine receptors in the pancreata of adult rats. The dissociation constant was 0.29 +/- 0.02 x 10(-9) M, and maximal binding capacity was 242 +/- 10 fmol of T3 bound per milligram of nonhistone protein at 30 degrees C (n = 20). Both parameters are comparable with those of adult rat liver nuclei. The degree of receptor occupancy was 30%-40% of the total sites in the adult rat pancreas. Developmentally, 3,5,3'-L-triiodothyronine binding was not detectable at birth and very low in pups less than 5 days old. It reached a peak at the third to fourth weeks. The degree of receptor occupancy changed with development from a low (19.2% +/- 2.0%) in 5-10-day-old pups to a high (50.5% +/- 3.0%) in 11-20-day-old pups, then returned to a moderate level (36.9% +/- 3.0%). The dissociation constants remained unchanged at various postnatal ages. Our data suggest that the rat pancreas is a target tissue for thyroid hormone and that thyroxine plays a role in pancreatic development.
Lee
J T
JT
Division of Gastroenterology, Children's Hospital, Buffalo, New York.
Lebenthal
E
E
Lee
P C
PC
D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D066298:In Vitro Techniques; D010179:Pancreas / Q000378:metabolism*; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011988:Receptors, Thyroid Hormone / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood
D011988:Receptors, Thyroid Hormone; D010664:Phenylmethylsulfonyl Fluoride; D013974:Thyroxine; D002118:Calcium