Hemodynamic and plasma atrial natriuretic factor responses to cardiac volume loading in young versus older normotensive humans

To assess the effects of age on responsiveness of atrial natriuretic factor (ANF) release, and the possible contribution of cardiac sympathetic activity, in young (n = 8) and older normotensives (n = 7), the effects of cardiac volume load on plasma ANF, central venous pressure, and general hemodynamics were evaluated. Studies were performed after pretreatment with placebo or 80 mg propranolol. Cardiac volume loading increased central venous pressure by 3–5 mmHg (1 mmHg = 133.3 Pa); β-blockade did not affect this response. Cardiac volume load caused significant increases in heart rate (10–15 beats/min) and cardiac index (by 0.7–0.8 L∙min−1∙m−2) and decreases in plasma catecholamines. Propranolol attenuated the increases in heart rate and cardiac index. These hemodynamic responses did not differ significantly between the two groups of subjects. Cardiac volume load significantly increased plasma ANF, by 87 ± 21 pg/mL in the young normotensives and by 212 ± 33 pg/mL in the older normotensives (p