Effect of triiodothyronine (T3) on ribonucleic acid polymerase activity in developing tadpole hindlimb.

Optimum conditions were studied for the determination of RNA polymerase activity in nuclei isolated from Rana catesbeiana tadpole hindlimbs. Tadpole nuclei were tested at 15 degrees C in the presence of spermidine (1.5 mM) bovine serum albumin (1.0%) and a high concentration of nucleoside triphosphates (1.0 mM). Tadpole nuclei exhibited a 60-70% higher total RNA polymerase activity with maximum activity of RNA polymerase I at 4 hr and RNA polymerase II at 8 hr after triiodothyronine injection. The results support a nuclear mechanism for the differentiation of tadpole hindlimbs induced by triiodothyronine.