Expression of thyroid hormone receptor isoforms in rat oligodendrocyte cultures. Effect of 3,5,3′-triiodo- l-thyronine

3,5,3′-Triiodo- l-thyronine (T 3) acts at the genomic level by interacting with nuclear T 3 receptors (T 3Rs). We have used double immunostaining to follow the expression of T 3Rs and oligodendrocytes (OL) lineage markers in rat secondary cultures consisting of 85–90% OL. Using antibodies against different synthetic peptides of T 3Rs (α common: α1 + α2 and β1) we find that α-T 3R is expressed in both O-2A progenitors and in mature OL, while β1-T 3R is expressed only in mature OL. In cultured OL, β1-T 3R mRNA is upregulated the most by T 3. OL exhibit more numerous and longer processes when treated by T 3.