Effects of changes in water-sodium balance on levels of atrial natriuretic factor messenger RNA and peptide in rats

Responses of atrial mRNA, atrial peptide and plasma peptide of atrial natriuretic factor (ANF) to treatments to alter fluid volume were studied in rats using RNA dot hybridization assay and radioimmunoassay. Specific changes in the level of ANF mRNA relative to total atrial RNA were observed in atria from sodium restricted rats and water deprived then sodium loaded rats, demonstrating an association of change in water-sodium balance with the expression of ANF gene. The levels of mRNA and the immunoreactive ANF in plasma decreased to 30% and 15% of controls, respectively, on water-deprivation and then increased again to control levels after administering 1.8% NaCl solution, whereas atrial immunoreactive ANF increased to about twice the control on water-deprivation and decreased again after supplying NaCl solution, in parallel with the level of the hematocrit. These findings suggest that atrial ANF content is dependent more on ANF release than on biosynthesis.