DEFICIENT TRANSCRIPTION OF SUBUNIT RPA-40 OF RNA-POLYMERASE-I AND RNA-POLYMERASE-III IN HEART OF RATS WITH NEONATAL ASPHYXIA

RNA polymerases transcribe nulcear genes for ribosomal RNA thus repres enting ribosomal biogenesis. RNA polymerase I transcribes class I gene s, coding for large ribosomal RNA and is located in the nucleolus. RNA polymerase III transcribes class III genes, those that encode a numbe r of small ribosomal RNA molecules. Both RNA polymerases form ribosoma l biogenesis in a concerted action and have a common subunit, RPA40, e ssential for function and integrity. The aim of our study was to study the influence of hypoxia/asphyxia on transcription of this subunit as deterioration of ribosomal biogenesis may not be compatible with life . To test this hypothesis we used a nonsophisticated model of neonatal asphyxia. Rat pups were exposed to various asphyctic periods up to tw enty minutes and heart tissue was taken for the evaluation of mRNA RPA 40 levels, pH measurements and histological evaluation of the nucleolu s by silver staining. mRNA RPA40 levels gradually decreased with the l ength of the asphyctic period paralleling the decrease of pH. Silver s taining was remarkably decreased at the asphyctic period of 20 minutes . Our findings of decreased transcription of this essential RNA polyme rase subunit indicate impairment of the ribosomal RNA synthetizing mac hinery and the histological findings suggest its structural relevance. This is the first in vivo observation of deteriorated RNA polymerase in asphyxia/hypoxia.