DEVELOPMENTAL-CHANGES IN MESSENGER-RNA ENCODING CARDIAC NA+ H+ EXCHANGER (NHE-1) IN RABBIT/

The faster recovery of cardiac contractility in newborn rabbit hearts during acute acidosis compared to adult hearts correlates with greater cellular activity of the Na+/H+ exchanger. We quantified mRNA encodin g Na+/H+ exchanger-1 (NHE-1) in rabbit ventricles of fetal (27 days ge station), newborn (2-5 days), and adult (>6 months) New Zealand white rabbits using reverse transcription-polymerase chain reaction (RT-PCR) and RNase protection assay, with GAPD mRNA as standard. Both RT-PCR a nd RNase protection assay revealed similar (p>0.05) cardiac levels of NHE-1 mRNA in fetal and newborn hearts, while NHE-1 mRNA in these hear ts was 1.7x and 1.6x greater than in adult hearts by both RT-PCR and R Nase protection assay. These developmental changes in NHE-1 mRNA corre late with the developmental changes in Na+/H+ activity in sarcolemmal vesicles purified from rabbit heart. (C) 1995 Academic Press,Inc.