Quantification of messenger ribonucleic acid for atrial natriuretic factor in atria and ventricles of Dahl salt-sensitive and salt-resistant rats.

Abstract

The levels of atrial natriuretic factor (ANF) and the mRNA for ANF were measured in the left ventricles of Dahl salt-sensitive (S) and salt-resistant (R) rats. ANF and ANF mRNA were both much higher in ventricular tissue of newborn rats of both strains compared to young adults, which represents the normal developmental pattern. There was no strain difference between S and R when the rats were young (1.5 months of age), but in older animals (8.5 months of age), when S rats were markedly hypertensive, there was a 5- to 10-fold increase in both left ventricular ANF and left ventricular ANF mRNA in S, but not R, rats. Atrial ANF mRNA was not similarly increased in hypertensive S rats. The ANF levels present in ventricles could not be accounted for by contamination with plasma ANF. Moreover, HPLC analysis of the forms of ANF in ventricles of newborn and hypertensive S rats showed that immunoreactive ANF in ventricles was present mainly in the same precursor form found in atria and not the shorter peptide form found in plasma. Northern blot analysis showed that ANF mRNA for atria and ventricles were the same size. It is concluded that in the S rat the heart left ventricle responds to hypertension by increasing production and storage of ANF.