FETAL ANTIGEN-1 (FA1), A CIRCULATING MEMBER OF THE EPIDERMAL GROWTH-FACTOR (EGF) SUPERFAMILY - ELISA DEVELOPMENT, PHYSIOLOGY AND METABOLISMIN RELATION TO RENAL-FUNCTION

We describe an ELISA technique for quantification of fetal antigen 1 ( FA1), a glycoprotein belonging to the EGF-superfamily. The ELISA is ba sed on immunospecifically purified polyclonal antibodies and has a dyn amic range of 0.7-5.3 ng/ml, intra-and inter-assay C.V.s of less than 3.2% and an average recovery of 105% in serum and 98% in urine. Compar ison of FA1 in amniotic fluid, serum and urine revealed parallel titra tion curves, identical elution volumes following size chromatography, immunological identity and similar profiles when analysed by MALDI-MS. The reference interval for serum FA1 was 12.3-46.6 ng/ml and the leve ls were 10 times higher in patients with renal failure. FA1 showed no diurnal variation, no variation during the menstrual cycle and was not influenced by the acute phase reaction. In humans (n = 10) the renal clearance of FA1 was 11 ml/min and an identical high renal clearance w as found in rats when expressed per 100 g body weight. In rats the ini tial increase in serum FA1 was 10 ng/ml/h following bilateral nephrect omy, explaining the increased serum concentrations of FA1 observed in patients with renal failure. (C) 1997 Elsevier Science Ireland Ltd.