Atrial natriuretic peptide and arginine vasopressin secretion in schizophrenic patients

Plasma levels of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) were measured in 15 patients with schizophrenic or schizoaffective disorders and 15 healthy volunteers during oral water loading at 20 ml/kg. In the patient group, plasma AVP was secreted even when plasma osmolality was below 270 mosmol/kg, although the sensitivity of AVP secretion response to osmolality was lower than in the controls. The ANP level was higher in the group of patients than in the controls. There was a negative correlation between plasma ANP and osmolality in the patients. We speculate that the volume expansion caused by inappropriate AVP secretion stimulated plasma ANP release and that the natriuresis resulting from the elevated plasma ANP level might contribute to hyponatremia.