Antidiuretic Principle in Malignant Tumor Extracts from Patients with Inappropriate ADH Syndrome¹

Abstract

Ten patients with malignant tumors and the classic manifestations of inappropriate ADH-syndrome were studied. The antidiuretic activity in the extracts of tumors and their metastases (10 patients), normal tissues (4 patients), and of plasma from 5 patients was measured by bioassay. The antidiuretic principle was also estimated by immunoassay. The nature of the antidiuretic material was investigated by 1) inactivation with vasopressinase system of human pregnancy plasma, 2) inactivation with vasopressin antiserum, 3) assaying for milkejection activity before and after incubation with vasopressin antiserum, and 4) attempting to measure vasopressor activity. Antidiuretic activity equivalent to that in 47–760 μU arginine vasopressin was found per mg tumor powder by bioassay in 5 patients. The values obtained by immunoassay were usually comparable to those of the bioassay. The results of the characterization studies of the antidiuretic principle indicate that it is either identical with or very similar to arginine vasopressin. The significance of these data is discussed.