Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The object of the research in this thesis was to demonstrate and characterize the actions of thyroid hormones at the cellular level. It was necessary to develop a cell culture system responsive to thyroid hormones. A method for the primary culturing of adult rat hepatocytes in serum-free medium is described. Culture surfaces were coated with a film of rat tail collagen which increased the longevity of the cells in culture. The addition of insulin or dexamethasone to the culture medium altered the morphology of the cells when compared to hepatocytes maintained in hormone-free medium. Insulin and dexamethasone, together, substantially improved the maintenance of morphology and longevity of the cells in culture. The addition of triiodothyronine, alone or with insulin and dexamethasone did not alter cell morphology or longevity.;Treatment of hepatocyte cultures with triiodothyronine in the presence of insulin and cortisol caused the concurrent inductions of mitchondrial (alpha)-glycerophosphate dehydrogenase and cytosolic malic enzyme which follow the same time course as the in vivo response to triiodothyronine. Hepatocytes isolated from thyroidectomized rats also respond to triiodothyronine with increased (alpha)-glycerophosphate dehydrogenase activity. Because hepatocyte cultures are only useful for short term studies (4 days), thyroid hormone actions on other enzymes, e.g. succinate dehydrogenase, NADPH-cytochrome c reductase and glucose-6-phosphatase, could not be fully characterized. The content of mitochondrial cytochromes a(+a(,3)), b and c were increased in hepatocytes by 3 days of triiodothyronine treatment. Thyroid hormone effects on glycerolipid synthesis were observed within 1 or 2 days of triiodothyronine treatment. The incorporation of choline into microsomal phospholipids was decreased by triiodothyronine. Triiodothyronine treatment increased glycerol incorporation into triglycerides but not into phospholipids of cultured hepatocytes. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI



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