Diabetes, hypophysectomy, or thyroidectomy reduces nuclear L-triiodothyronine-binding capacity of rat lung

L-T3 (T3) receptors of the lungs of rats were found to be under hormonal control. The apparent binding capacity of T3 receptors of lungs of diabetic, hypophysectomized, and thyroidectomized rats were 0.224 +/- 0.009, 0.195 +/- 0.007, and 0.102 +/- 0.008 pmol/mg DNA, as compared to 0.0321 +/- 0.014 pmol/mg DNA for normal animals. The binding affinities for T3 in normal, diabetic, hypophysectomized, and thyroidectomized rats were 256 +/- 3.24, 270 +/- 3.81, 249 +/- 4.03, and 260 +/- 8.2 pM, respectively. The magnitude of the maximum binding capacity in these cases was apparently not due to the loss of either T3 receptors or DNA during the incubation. Serum T3 and T4 concentrations in normal rats were 120.0 +/- 7.2 ng/dl and 5.9 +/- 0.5 micrograms/dl, respectively. Diabetes, hypophysectomy, and thyroidectomy lowered these values to 79 +/- 5.4, 60 +/- 5.8, and 30 +/- 1.6 ng/dl for T3 and 3.5 +/- 0.3, 2.7 +/- 0.4, and 1.9 +/- 0.2 micrograms/dl for T4, respectively.