Atrial natriuretic polypeptide after burn injury: blood levels and physiological role in rats

To define the relationship between atrial natriuretic polypeptide and the physiological changes of water and electrolytes after burns, the changes in plasma hormonal levels, including atrial natriuretic polypeptide, and urinary water and sodium excretions were examined in burned rats. Further, to elucidate the physiological significance of atrial natriuretic polypeptide after burns, the effects of a specific antiserum against atrial natriuretic polypeptide were determined in burned rats. Plasma atrial natriuretic polypeptide levels in rats following 30 per cent BSA full skin thickness burns were elevated for sustained periods (432.3 +/- 156.5 pg/ml, P less than 0.01 on day 1 postburn, 244.5 +/- 73.7 pg/ml, P less than 0.05 on day 3 postburn). Urine volume and sodium excretion decreased significantly during the first 72 h after burns. On day 3 postburn, urine volume and sodium excretion began to increase significantly. Specific rabbit antiserum against atrial natriuretic polypeptide was injected into the burned rats during this diuretic phase. Significant inhibition of diuresis and natriuresis was observed after the injection of antiserum (27.5 +/- 2.4 per cen decrease in urine volume, 57.1 +/- 10.4 per cent decrease in sodium excretion). These results suggest that atrial natriuretic polypeptide plays a physiological role in the regulation of urinary water and sodium excretion after burns.