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Isolated heart-lung preparations from hypertensive inbred Dahl salt-hypertension sensitive (S) and normotensive inbred Dahl salt-hypertension resistant (R) rats were perfused using 15% washed rat red blood cells in Krebs-Ringer bicarbonate buffer. Atrial pressures were increased by increasing venous return (preload) or by increasing the arterial resistance (afterload). Increases in preload at a constant afterload produced increases in the right and left atrial pressures equivalent between S and R strains. Atrial natriuretic factor (ANF) release was linearly related to right atrial pressure (RAP) or left atrial pressure (LAP) in either strain, but S released more ANF at each level of preload, and the slope of the line relating ANF release to RAP was significantly greater in S than R. When the heart-lung preparations were subjected to changes in afterload at a constant preload, LAP was significantly increased in R but not in S rats, and concomitantly ANF increased in R but not in S. In the afterload experiments, as in the preload studies, S released more ANF than R for comparable LAP. It is concluded that 1) at any atrial pressure, hearts of hypertensive S rats release more ANF than hearts of normotensive R rats, 2) this strain difference is probably a consequence of hypertension, and 3) the observed relationships between ANF release and atrial pressures support the contention that atrial distention stimulates the release of ANF.
Onwochei et al. (1987) studied this question.