Atrial natriuretic peptide during acute and prolonged exercise in well-trained men.

In this study, cardiac performance and circulating immunoreactive atrial natriuretic peptide (Ir-ANP) were measured during sustained exercise to examine the relationship between cardiac filling, heart rate and circulating ANP. Fifteen well-trained male subjects (mean age = 27.6 +/- 1 years) were studied during two exercise sessions. Initially, graded exercise to maximum was performed to determine maximal oxygen consumption (VO2max). On a separate occasion subjects performed 150 minutes of continuous exercise at 70-74% of the maximal heart rate, with radionuclide angiography performed at rest and every 50 minutes, in conjunction with Ir-ANP, blood pressure and heart rate measurements. During maximal exercise subjects reached a VO2max of 47.9 +/- 2.1 ml/kg/min. Ir-ANP increased from 9.8 +/- 1.1 pg/ml at rest to 45.2 +/- 6.6 pg/ml at maximal exercise. Ir-ANP remained elevated (28.9 +/- 3.4 pg/ml) 3 minutes after exercise (p < 0.05). During prolonged exercise, left ventricular end-diastolic filling decreased significantly between 50 and 150 minutes (p < 0.05), with progressive rise in heart rate observed between 50 (141 +/- 8 beats/minute) and 150 minutes (154 +/- 3 beats/min; p < 0.05). No change in left ventricular end-systolic counts, or arterial blood pressure were observed throughout the exercise period. Ir-ANP was elevated significantly during prolonged exercise, increasing from 9.4 +/- 1.7 at rest, to 19.2 +/- 3.4 after 50 minutes, 17.8 +/- 4.3 pg/ml after 100 minutes of exercise (p < 0.05), and 23.5 +/- 2.1 pg/ml by 150 minutes of exercise. A weak correlation (r = 0.33) was observed between heart rate and Ir-ANP throughout the exercise session.(ABSTRACT TRUNCATED AT 250 WORDS)