Digoxin-like immunoreactive substance in urine of patients with mucocutaneous lymph node syndrome (MCLS).

Levels of digoxin-like immunoreactive substance (DLIS) and dehydroepiandrosterone sulfate (DHEA) in urine from patients with mucocutaneous lymph node syndrome (MCLS) were measured by radioimmunoassay. Because DLIS of stored samples was often below the level of detection by conventional immunoassay, the authors used 80% ammonium sulfate and extraction with phosphate buffer and then 80% hot ethanol. To study the origin of raised levels of DLIS in urine, the synthesis of DLIS by cultured human umbilical vein endothelial cells (HUVEC) was tested in vitro. The correlation between DLIS and DHEA levels was not significant. Mean levels of urinary DLIS corrected for creatinine in the patients with MCLS were significantly higher than in both normal and diseased controls. The culture medium of HUVEC was found to contain DLIS activity. These results show that MCLS should be added to the clinical states associated with an increased urinary concentration of DLIS and that the endothelial cells are one source of DLIS in man.