SECRETION OF ATRIAL-NATRIURETIC-PEPTIDE AND VASOPRESSIN BY SMALL-CELLLUNG-CANCER

Background. Hyponatremia in patients with small cell lung cancer (SCLC ) is a common clinical problem usually attributed to tumor secretion o f arginine vasopressin (AVP). It recently was shown that some SCLC cel l lines produce atrial natriuretic peptide (ANP). The purpose of this investigation was to determine the frequency and clinical consequences of secretion of ANP by SCLC and the relative contribution of ANP and AVP to the hyponatremia associated with this disease. Methods. Levels of ANP and AVP were measured in 23 SCLC cell lines and 23 other human tumor cell lines. Also, ANP and AVP levels were determined in plasma s amples from 69 patients with active small cell carcinomas. Results. Of the 23 SCLC lines, 16 (70%) had elevated ANP levels. Only two (8.7%) had elevated AVP levels, and these two also had elevated ANP levels. O ne of the ANP-producing cell lines was derived from a hyponatremic pat ient with no other apparent explanation for a low sodium level. Howeve r, the four cell lines with the highest levels of ANP were derived fro m patients who were not hyponatremic. Two other human tumor lines also produced ANP. Of the 69 patients with SCLC, 21 (30.4%) had elevated A NP levels, whereas 4 (6%) had elevated AVP levels. Fifteen of these pa tients were hyponatremic during their clinical course (21.7%). Of the eight patients who were hyponatremic when samples were collected, two had elevated ANP levels, and only one had elevated AVP levels. Six pat ients (8.7%) had symptoms of postural hypotension, possibly attributab le in some cases to tumor secretion of ANP. Conclusions. The majority of SCLC lines produce ANP, and a minority produce AVP. Secretion of AN P may result in hyponatremia and/or postural hypotension. However, sec retion of either or both of these peptides does not account for all ca ses of hyponatremia in patients with SCLC and does not necessarily cau se clinical manifestations.