Effects of various pathological conditions on the nuclear T3 receptors of rat cerebral cortex: comparison with liver.

The binding capacity and relative affinities of the nuclear triiodothyronine receptors were measured in the cerebral cortex and liver tissues of the rat under several conditions involving energy deprivation. Protracted hypothyroidism caused significant increases in binding capacity in both brain and liver representing a probable direct tissue response to this specific thyroidal dysfunction. Three conditions affecting glucose homeostasis: fasting, glucagon administration and insulin-induced acute hypoglycemia, caused a significant decrease in nuclear binding capacity measured by in vitro binding assay in liver but did not affect brain receptors indicating a tissue specific response to these altered energy states. Lowering of available oxygen (hypoxia) also appeared to cause a slight decrease in binding capacity in the cerebral cortex measured in vitro. On the other hand, total depletion of oxygen (anoxia) showed a progressive increase in binding of a lower affinity nature in the cerebral cortex and liver. A similar change in binding and affinity was seen in the progression of the post-mortem condition in the cerebral cortex and liver resulting from a probable general alteration of the chromosomal material. These results illustrate the degree and nature of alterations of a specific nuclear regulatory component, the thyroid hormone receptor, under several pathological conditions.