Effect of Thyroid Hormone on Insulin Action in Cultured Arterial Smooth Muscle Cells

Summary

The effect of triiodothyronine (T₃) on insulin action in cultured smooth muscle cells of the rat aorta were studied. Insulin binding to smooth muscle cells was increased by T₃. The Scatchard analysis indicated an increase of insulin binding sites and an elevation of the affinity of insulin to its binding sites. T₃ alone had no significant effect on DNA, RNA and protein synthesis in smooth muscle cells and did not increase the transport of 3-O-methylglucose into the cells. However, the insulin-induced 3-0-methylglucose transport into the cells was stimulated. The insulin-stimulated protein synthesis was not significantly altered by T₃ treatment, whereas the effect of insulin on DNA and RNA synthesis was even reduced in the presence of T₃. The study suggests, that T₃ treatment produces predominantly a stimulation of processes which are necessary for the production of energy. The anabolic effect of insulin is decreased and must by inferior to the credit of energy production.

Key-Words:

Insulin - Thyroid Hormone - Smooth Muscle Cells