Ontogenesis of nuclear T3 receptors in primary cultured astrocytes and neurons.

ABSTRACT

Nuclear T3 receptor (NTR) have been characterized in separated cultures of neurons and astrocytes. Scatchard analysis indicated the presence of a single class of high-affinity sites in both cell lines. The apparent equilibrium association constant ranged from 1.80 +/- 0.41 X 10(10) M-1 to 3.27 +/- 0.74 +/- 10(10) M-1 in neurons and from 1.01 +/- 0.09 to 1.80 +/- 0.73 X 10(10) M-1 in astrocytes depending on the time in culture. In neurons, the maximal binding capacity (MBC) increased from 0.049 +/- 0.008 ng T3/mg DNA to 0.328 +/- 0.052 ng T3/mg DNA between 3 and 12 days of culture. In astrocytes, the changes in MBC were less pronounced ranging from a minimum of 0.095 +/- 0.024 ng T3/mg DNA at the 7th day of culture to a maximum of 0.198 +/- 0.048 ng T3/mg DNA at the 21st day. The relative binding affinity of the receptor for thyroid hormone analogs was in the order TRIAC greater than L-T3 greater than D-T3 greater than L-T4 in both cell lines. These results show that nuclear T3 receptors similar to those found in vivo are present in primary cultures of both astrocytes and neurons.