Regulation of and actin mRNA by thyroid hormone in the developing rat brain

Abstract

The relative sensitivity of the two isotypes of actin mRNA (β and γ ) to thyroid hormone (T₃) was examined by comparing the steady state levels of these mRNAs with their rates of transcription in cerebra from normal and hypothyroid rats of different ages, covering the period of synaptogenesis (days 1-20 postnatal). Hypothyroidism was associated with a reduction in the steady state level of β-actin mRNA during the entire period, but levels of γ-actin mRNA were reduced only during the early phase of synaptogenesis (first week). The rats of transcription of both β- and γ-actin mRNAs were stimulated by T₃ during the early phase but that of β-actin mRNAs was relatively more sensitive to T₃ than γ-actin mRNA. The lack of correlation between the rates of transcription of β- and γ-actin mRNA at different ages with their corresponding steady-state levels suggests additional post-transcriptional regulation.