Atriopeptin release in conditions of altered salt and water balance in the rat

Manipulations of salt and water intake influenced the atriopeptin content in the atria and plasma of rats. Plasma levels of atriopeptin varied in proportion with dietary salt intake. In contrast, cardiac levels of atriopeptin varied inversely with the amount of salt in the diet. Acute stimulation of atriopeptin release can be produced by treatments which elevate atrial pressure, including atrial stretch, volume overloading, water immersion, and vasoconstrictor agents. Vasopressin-stimulated atriopeptin release preferentially depleted right atrial stores. In spite of the initial differences in cardiac stores of atriopeptin in the rats on different diets, there were no major differences in the amount of atriopeptin released in response to vasopressin stimulation. These data suggest that there is a functional excess of cardiac atriopeptin stores. We also examined the atrial and plasma atriopeptin content in the Dahl salt-sensitive and resistant rats to determine whether the development of hypertension in the Dahl sensitive rats is associated with abnormalities in basal or stimulated levels of atriopeptin. The effects of dietary salt intake on basal and stimulated atriopeptin levels in both the Dahl sensitive and resistant rats were similar to those observed in normal rats, suggesting that abnormalities in atriopeptin content do not contribute to the etiology of hypertension in the Dahl salt-sensitive rat.