Thyroid hormone-induced GLUT-1 expression in rat cerebral tissue: effect of age.

To determine if thyroid hormone (TH) modulates the expression of cerebral glucose transporter one (GLUT-1) and whether there are age-related differences in TH effect, young male Fischer 344 rats (6 months old) and aged rats (26 months old) were studied at euthyroid, hyperthyroid and hypothyroid conditions. Immunoblot analysis indicated that 55 kDa GLUT-1 mass was decreased in hypothyroid young rats (174 +/- 15 arbitrary units) and hyperthyroid rats (144 +/- 22) compared to euthyroid young rats (395 +/- 57) P < 0.01. Jr. aged rats the 55 kDa GLUT-1 mass was significantly increased in hyperthyroidism (392 +/- 49) compared to euthyroid aged rats (237 +/- 27) P < 0.05. The 45 kDa isoform of GLUT-1 in rat cerebral tissue did not significantly change with age or thyroidal state. The changes in 55 kDa GLUT-1 mass did not correlate with the changes of GLUT-1 mRNA content. It is concluded that alterations in cerebral GLUT-1 content in response to altered thyroid state are age-specific.