Differential induction of fos and jun family genes by thyrotropin in rat thyroid FRTL-5 cells.

Effect of thyrotropin (TSH) on the expression of the members of fos and jun family genes in a rat thyroid cell line (FRTL-5) was examined by the reverse transcription-polymerase chain reaction (RT-PCR) method. FRTL-5 cells were maintained in a TSH-deprived medium for 5 days. After 1 mU/mL TSH addition, the cells were harvested at intervals. Total RNA extracted from the cells was subjected to RT-PCR. TSH induced a rapid and transient expression of c-fos, fosB, and fra-1 with different kinetics. Increase in c-fos mRNA was most rapid with a peak level at 30 min after TSH addition. The fosB mRNA reached a peak level at 60 min poststimulation with a rapid decline at 90 min. The fra-1 mRNA increased at 60 min followed by a gradual decrease until 120 min. The change in fra-2 mRNA level was similar to that of fra-1. TSH induced similar changes in the levels of c-jun and junB mRNAs. They significantly increased within 30 min followed by a sustained high level until 90 min. The differential induction of fos and jun family genes suggests an important role of their gene products on the regulation of thyroid cell function by TSH.