Humoral adaptation to experimental heart failure

Sequential changes in mean aortic pressure, plasma renin activity, plasma aldosterone concentration, urinary sodium excretion, and plasma volume in a dog with moderate thoracic inferior vena cava constriction. There is initial hypotension, activation of the renin-angiotensin-aldosterone system, and a marked reduction in urinary Na+ excretion. By day 7, however, a new steady state is achieved in which renin and aldosterone levels and Na+ excretion have returned to baseline levels. The associated plasma volume expansion is responsible for restoring venous return to the heart, thereby allowing systemic hemodynamics to be normalized.