NUCLEAR 3,5,3'-TRIIODOTHYRONINE RECEPTORS (T_2R) IN CIRCULATING HUMAN LYMPHOCYTES FROM NORMAL, HYPER- AND HYPOTHYROID SUBJECTS

In order to investigate the relationship between the nuclear receptors and thyroid functions, we have determined the circulating lymphocyte nuclear T_3R in normal subjects, in patients with hyper-and hypothyroidism and in hypothyroid patients on thyroid hormone substitution therapy. In hyperthyroid and hypothyroid patients, the nuclear affinity (kd) for T_3 was similar to that of normal subjects. In hyperthyroidism maximal binding capacity (MBC) of nuclear T_3R was unaltered, whereas in hypothyroidism the MBC was significantly increased up to 8.06±0.80 fmol/μg DNA, which was 2.1 times that of the control group. In hypothyroid patients treated with 90—120 mg desiccated thyroid daily the nuclear MBC was 4.34±0.72fmol/μg DNA, not different from that observed in euthyroid subjects. It was found that the nuclear T_3R MBC was negatively correlated with serum levels of T_3, T_4, FT_3, FT_4 and rT_3, but positively correlated with serum TSH concentration in hypothyroid patients. These results indicated hormonal modulation of the nuclear T_3R which exhibited up regulation in hypothyroidism. The increase in nuclear T_3R number might reflect a compensatory mechanism for the maintenance of cellular homeostasis in face of decreased serum concentrations of thyroid hormones.

NUCLEAR 3,5,3'-TRIIODOTHYRONINE RECEPTORS (T_2R) IN CIRCULATING HUMAN LYMPHOCYTES FROM NORMAL, HYPER- AND HYPOTHYROID SUBJECTS