Atrial natriuretic peptide (ANP) has known natriuretic, diuretic, and vasodilatatory effects. It is synthesized and stored in the atrial cells. Stretching of the atrial muscle fibers during an increase in venous return sets a response of ANP release into the blood stream. High levels of ANP were measured in a number of lung diseases. Pneumonia in children is frequently accompanied by the hyponatremia of the syndrome of inappropriate antidiuretic hormone (ADH) secretion (SIADH). High levels of ANP were found among patients with SIADH. Our objective was to determine if ANP plasma levels are altered in children with pneumonia, and to evaluate a possible correlation between severity of pneumonia and ANP levels. Blood samples from 28 children diagnosed with pneumonia were collected. Plasma ANP levels were determined by radioimmunoassay and compared to levels in 25 children without pneumonia. ANP levels in the pneumonia group (mean +/- SD, 16.02 +/- 11.69 pg/ml) increased significantly (P < 0.01) compared to levels in the control group (mean +/- SD, 7.44 +/- 9.29 pg/ml). Children in the pneumonia group also exhibited low levels of plasma sodium (mean +/- SD, 134.88 +/- 2.5 mmol/l) compared to levels in children without pneumonia (mean +/- SD, 139.77 +/- 4.15 mmol/l) (P < 0.01). There was no correlation between ANP plasma levels and severity of pneumonia. In conclusion, ANP levels in children with pneumonia, as in other lung diseases, are increased. High ANP levels may play a role in maintaining water and electrolyte equilibrium during a state of inappropriate ADH secretion accompanying pneumonia.
2005 Wiley-Liss, Inc.