Hiroko Hara

Significant increase in plasma immunoreactive atrial natriuretic polypeptide concentration during head-out water immersion

To investigate the physiological regulatory mechanism of human atrial natriuretic polypeptide (hANP) secretion, plasma hANP was measured by a direct radioimmunoassay during head-out total body water immersion (WI) in normal men. Five healthy men were immersed in water for 1 hr. Urine volume and Na excretion were significantly increased during WI. Plasma hANP increased significantly during WI peaking at 30 min. and returned toward the baseline after WI. Plasma renin activity and norepinephrine were suppressed occasionally during WI. Plasma ADH did not change throughout the study period. Maximal increments in plasma hANP correllated with that in urine output or urinary Na excretion during WI. These data suggest that acute central hypervolemia caused by WI increases hANP secretion and that this increase may participate in the diuretic response to WI.

Hemodynamic, renal, and hormonal responses to alpha‐human atrial natriuretic peptide in patients with congestive heart failure

Hemodynamic, renal, and hormonal effects of intravenous bolus injection of 50 µg synthetic α‐human atrial natriuretic peptide (α‐hANP) were studied in eight patients with congestive heart failure. α‐hANP caused significant reductions in mean blood pressure and systemic vascular resistance. These responses were sustained up to 90 minutes and not accompanied by reflex tachycardia. Cardiac index and stroke volume index increased significantly at 90 minutes and pulmonary capillary wedge pressure, pulmonary arterial pressure, and mean right atrial pressure remained unchanged. Urine volume, urinary sodium excretion, creatinine clearance, and fractional excretion of sodium increased significantly, but fractional excretion of potassium and phosphate did not change. Elevated plasma renin activity, plasma aldosterone, and norepinephrine were suppressed after the injection of α‐hANP. The bolus injection of this peptide has moderately hypotensive, vasorelaxant, and natriuretic effects in patients with congestive heart failure.

Changes in the plasma hANP level during long-term salt loading in patients with essential hypertension

Serial changes in the plasma hANP (human atrial natriuretic peptide) level in patients with essential hypertension were determined during high salt intake for two weeks after salt restriction for 5 days. The mean plasma hANP level decreased during salt depletion for 5 days from 60 +/- 10 pg/ml to 39 +/- 8 pg/ml. During high salt intake (20 g NaCl/day) for two weeks, the plasma hANP level increased gradually to a maximum of 71 +/- 16 pg/ml on day 7 and then decreased to 54 +/- 9 pg/ml on day 14. The plasma levels of renin activity, aldosterone and noradrenaline decreased during salt repletion. Changes in the plasma hANP level were correlated positively with those of urinary sodium excretion and negatively with those of plasma renin activity on days 7 and 14 of salt repletion. Change in the plasma hANP level correlated with that in the mean blood pressure on day 14, but not day 7 of salt repletion. These findings indicate that the plasma hANP level is closely related to sodium intake in patients with essential hypertension.