Response of atrial natriuretic factor to acute extracellular fluid volume expansion in patients with pheochromocytoma

Background. Patients with pheochromocytoma have been reported to show high plasmatic atrial natriuretic factor (ANF) levels. Its source may not be the atrium because blood volume, the most important physiological stimulus for ANF release, is usually reduced in these patients. Methods. To evaluate ANF secretion functional integrity, we studied three p atients with pheochromocytoma before and after surgical removal of the tumo r. Extracellular fluid (ECF) volume, plasmatic ANF levels, and plasmatic re nin activity (PRA) were measured. ANF was measured before and after an acut e saline load of 1.5 L in 90 min. Results. Before surgery, ECF volume was normal or reduced, and PRA was norm al and decreased after the saline load. By contrast, ANF was elevated and d id not change after the saline load. After surgery ANF decreased, ECF volum e rose, and the saline load induced a significant increase of plasma ANF an d reduction of PRA. ANF was present in significant amounts in tumoral tissu e homogenates. Conclusions. These data suggest that the tumor was the source of ANF in the se patients with pheochromocytoma because high levels of ANF, despite reduc ed or normal ECF volume, as well as unresponsiveness to acute saline infusi on, were found before surgery with subsequent normalization after tumor rem oval. (C) 2001 IMSS. Published by Elsevier Science Inc.