Atrial natriuretic peptide and plasma volume of dogs suffering from heart failure or dehydration.

Studies in humans and experimental animal models suggest that volume overload increases and volume underload decreases release of atrial natriuretic peptide (ANP), a hormone intimately linked to water and electrolyte homeostasis. This relationship was examined in dogs suffering from heart failure or dehydration and the data presented here are in support of this general concept. Plasma ANP concentration in dogs with congestive heart failure (CHF) was elevated with the severity of the disease (NYHA classification, class II: 21.4 +/- 9.2 fmol ANP/ml; class III: 65.5 +/- 72.6; class IV: 119.7 +/- 87.1; healthy dogs: 13.9 +/- 7.5). The increment in plasma ANP concentration in cardiac patients was also positively correlated with the plasma volume. The blood volume of dogs with moderate and severe CHF was significantly (P < 0.05) elevated and a normotonic blood pressure prevailed. In contrast, dehydrated dogs tend to display reduced ANP plasma concentration (7.7 +/- 5.6 fmol/ml) as well as significantly lower plasma volume and reduced blood pressure (P < 0.05). In dogs with severe CHF, ANP precursor material is present in the blood, which is normally undetectable. These data further support the concept of a regulatory function of ANP in volume homeostasis of dogs.