CHARACTERISTICS OF ATRIAL NATRIURETIC HORMONE RECEPTORS IN HUMAN PHEOCHROMOCYTOMAS

The presence of functional receptors for human atrial natriuretic hormone in human pheochromocytomas was recently reported. The present study reports the binding of hANH as measured by Scatchard analysis in 4 human adrenal glands and in 5 human pheochromocytomas. Binding assays using [3H]ANH revealed a single class of high-affinity binding sites for hANH in both tissues. Human pheochromocytomas present a lower number of binding sites than normal human adrenal gland (B(max) of 7.1 ± 2.1 vs 33.6 ± 6.9 fmol/mg protein, respectively). However, the decreased number of ANH receptors was not paralleled by modifications of tissular cyclic GMP (cGMP). Moreover, plasma hANH concentrations in 7 patients with pheochromocytomas (20.2 ± 2.7 pmol/l) were statistically higher than those obtained in 25 normal control humans (8.1 ± 0.6 pmol/l, p <0.001). We also demonstrated the presence of immunoreactive ANH in the tumour itself.