PHENYLETHANOLAMINE N-METHYLTRANSFERASE MESSENGER-RNA IN RAT SPLEEN AND THYMUS

Phenylethanolamine N-methyltransferase (PNMT), the final enzyme in the biosynthesis of epinephrine, has been detected in rat and human splee n with radioenzymatic assays, but the presence of PNMT has not been ex amined in other lymphoid tissues. Using the reverse transcription poly merase chain reaction (RT-PCR) and Southern blot analysis, we tested f or PNMT mRNA in rat spleen and thymus. A single PCR fragment from sple en, thymus, adrenal and brainstem gave a strong hybridization signal w ith a PNMT cDNA probe, whereas a PCR fragment from liver was only fain tly visible on Southern blots. These findings indicate that the PNMT g ene is expressed in spleen and thymus and raise the possibility that l ymphoid organs synthesize epinephrine as an intrinsic regulator. (C) 1 998 Elsevier Science Ireland Ltd.