T3 rapidly modulates TSHβ mRNA stability and translational rate in the pituitary of hypothyroid rats

Whereas it is well known that T3 inhibits TSHβ gene transcription, its effects on TSHβ mRNA stability and translation have been poorly investigated. This study examined these possibilities, by evaluating the TSHβ transcripts poly(A) tail length, translational rate and binding to cytoskeleton, in pituitaries of thyroidectomized and sham-operated rats treated with T3 or saline, and killed 30 min thereafter. The hypothyroidism induced an increase of TSHβ transcript poly(A) tail, as well as of its content in ribosomes and attachment to cytoskeleton. The hypothyroid rats acutely treated with T3 exhibited a reduction of TSHβ mRNA poly(A) tail length and recruitment to ribosomes, indicating that this treatment decreased the stability and translation rate of TSHβ mRNA. Nevertheless, acute T3 administration to sham-operated rats provoked an increase of TSHβ transcripts binding to ribosomes. These data add new insight to an important role of T3 in rapidly regulating TSH gene expression at posttranscriptional level.