Abstract
Aging is associated with numerous alterations in thyroid hormone homeostasis. Because T3 accounts for much of the peripheral metabolic effect of thyroid hormone, and T4, to T3 conversion has been shown to be altered by fasting, at least in nonsenescent rats, the effect of age on this aspect of thyroid hormone metabolism was assessed. In the fed state, increasing age did not alter T4, to T3 conversion by rat liver homogenate (5.03 ± 0.7 vs. 4.44 ± 0.8%)(mean ± SD). Age did, however, alter the peripheral thyroid hormone response to fasting. Liver homogenates from fasted mature rats produced approximately 74% the amount of T3 generated by tissues from similarly aged fed controls (p < 0.001). Fasting did not, however, decrease the amount of T3 generated by liver homogenates from senescent rats. The in vitro addition of 5 mM dithiothreitol (DTT) increased T3 generation 60.7 ± 9.0% (mean ± SD) (p < 0.001) by tissues from fed mature rats; DTT (5 mM) did not alter T4, to T3 conversion by tissues from fed aged rats. DTT (5 mM) added to tissues from fasted mature rats eliminated the decline in T3 generation associated with fasting. DTT (5 mM) had no effect on tissues from fasted senescent rats. In conclusion, in the fed state, increasing age does not alter T4, to T3 conversion by rat liver homogenate. Age does alter the peripheral thyroid hormone response to fasting.
Similar content being viewed by others
References
Ingbar, S. H.: Effect of aging on thyroid hormone economy in man. J. Amer. Geriatrics Soc., 24:49–53, 1976.
Gaffney, G. W., Gregerman, R. I., Shock, N. W.: Relationship of age to the iodide in euthyroid man. J. Clin. Endocrinol. Metab., 22:784–794, 1962.
Gaffney, G. W., Gregerman, R. I., Yiengst, M. J., Shock, N. W.: Serum protein bound iodine concentration in blood of euthyroid man aged 18 to 94 years. J. Geront., 15:234, 1960.
Wenzel, K. W., Horn, W. R.: Triiodothyronine (T3) and thyroxine (T4) kenetics in aged men. Excerpta Medica, 361:89, 1975.
Gregerman, R. L., Gaffney, G. W., Shock, N. W.: Thyroxine turnover in euthyroid man with special reference to changes with age. J. Clin. Invest., 41:2065–2074, 1962.
Braverman, L. E., Dawber, N. A., Ingbar, S. H.: Observations concerning the binding of thyroid hormones in sera of normal subjects of varying ages. J. Clin. Invest., 45:1273–1279, 1966.
Hermann, J., Rusch, H. J., Kroll, H. J., Hilger, P., Kruskemper, J. L.: Free trliodothyroxine (T3) and thyroxine (T4) serum levels in old age. Horm. Metab. Res., 6:239–240, 1974.
Bermudez, F., Surks, M. I., Oppenheimer, J. H.: High incidence of decreased serum triiodothyronlne concentration in patients with nonthyroidal disease. J. Clin. Endocrinol., 41:27–40, 1975.
Gambert, S. R., Ingbar, S. H., Hagen, T. C.: Interaction of age and thyroid hormone status on Na+-K+ ATPase in rat renal cortex and liver. Endocrinology, 108:27–30, 1981.
Denckla, W. D.: Role of the pituitary and thyroid glands in the decline of minimal O2 consumption with age. J. Clin. Invest., 53:572–576, 1974.
Ingbar, S. H., Braverman, L. E.: Active form of the thyroid hormone. Ann. Rev. Med., 26:443–449, 1975.
Suda, A. K., Pittman, C. S., Shimlzu, T., Chambers, J. B.: Production and metabolism of 3,5,3′-triiodothyronine and 3,3′,5′-triiodothyronlne in normal and fasting subjects. J. Clin. Endocrlnol. Metab., 47:1311–1319, 1978.
Harris, A. R., Fang, S. L., Hinerfeld, L., Braverman, L. E., Vagenakls, A. G.: The role of sulfhydryl groups on the impaired hepatic 3′,3,5-triiodothyronlne generation from thyroxine in the hypothyroid, starved, fetal and neonatal rodent. J. Clin. Invest., 63:516–524, 1979.
Kaplan, M. M., Utiger, R. D.: Iodothyronine metabolism in rat liver homogenates. J. Clin. Invest., 61: 459–471, 1979.
Utiger, R. D.: Serum triiodothyronine in man. Ann. Rev. Med., 25:289–294, 1974.
Stohs, S. J., Hassing, J. M., Al-Turk, W. A., Masoud, A. N.: Glutathione levels in hepatic and extrahepatic tissues of mice as a function of age. AGE, 2:11–14, 1980.
Balsam, A., Ingbar, S. H.: Observations on the factors that control the generation of triiodothyronine from thyroxine in rat liver and the nature of the defect induced by fasting. J. Clin. Invest., 63:1146–1146, 1979.
Lowry, O. H., Rosebrough, N. J., Farr, A. C., Randall, R. J.: Protein measurement with the Folin phenol reagent. J. Biol. Chem., 193:265–275, 1951.
Author information
Authors and Affiliations
About this article
Cite this article
Gambert, S.R. Effect of age on the conversion of thyroxine (T4) to 3,5,3′ triiodothyronine (T3) by liver homogenate from fed and fasted Sprague-Dawley rats. AGE 5, 88–91 (1982). https://doi.org/10.1007/BF02431713
Issue Date:
DOI: https://doi.org/10.1007/BF02431713