Strain-specific differences in transcription of the gene for the epinephrine-synthesizing enzyme phenylethanolamine N-methyltransferase

Abstract

Phenylethanolamine N-methyltransferase (PNMT), the enzyme which synthesizes the catecholamine epinephrine (adrenaline), may be regulated at many levels of expression. This study examines one level, the production of PNMT hnRNA, by measuring its rate of transcription in the rat adrenal gland and bovine adrenal medulla using an in vitro nuclear transcription run-on assay. Furthermore, when the transcriptional rate is compared in strains of rat known to possess distinctive levels of epinephrine and PNMT enzyme, the rate of PNMT transcription in Fischer rats is greater than in Buffalo or Sprague-Dawley rats: relative ratios are 0.54:1.00:1.6 for Buffalo:Sprague-Dawley:Fischer adrenal glands. As such, it appears that the rate of PNMT gene transcription is the major factor responsible for the strain-specific levels of PNMT mRNA among these rats. Therefore, in addition to regulation by neural and steroid influences, an intrinsic genetic component also governs the level of PNMT gene expression.