title: Thyroid hormone regulation of beta-adrenergic receptor number in aging rats.
abstract: To evaluate the capacity of the myocardium in aged rats to respond to hyperthyroidism, we quantified myocardial beta-adrenergic receptors in female Fischer 344 rats of 3, 12, and 24 months of age. In T3-treated rats (500 microgram T3/kg . day for 3 days), myocardial beta-adrenergic receptors, as measured by [3H]dihydroalprenolol binding, were significantly increased (P less than 0.01) over controls in 3-, 12-, and 24-month-old animals. The data demonstrate that senescent rats retain the capacity to increase myocardial beta-adrenergic receptors in response to exogenous hyperthyroidism. In the myocardium, the mechanism of decreased catecholamine responsiveness in aging appears to be at other than the beta-adrenergic receptor site, since receptor density is unaltered with age, as is receptor modulation in response to hyperthyroidism.
mesh_terms: D000375:Aging; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004082:Dihydroalprenolol / Q000378:metabolism; D005260:Female; D006321:Heart / Q000254:growth & development*; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D014284:Triiodothyronine; D004082:Dihydroalprenolol