Direct radioimmune assay of 16-glucosiduronate metabolites of estriol in human plasma and urine.

It has been established that the 16-glucosiduronate metabolites of estriol comprise the major estriol component in pregnancy plasma [ 1 ] , urine [ 1,2] and amniotic fluid [3]. However, little is known about their physiological or pathological correlations. One reason is the fact that assays for individual metabolites of estriol either do not exist or are unsuitable for practical processing of large numbers of clinical samples. The possibility that immune assays might provide a useful means of measuring individual estriol metabolites prompted us to develop and investigate various antigens. A non-specific 16a-glucosiduronate antiserum has been reported [4]. This report describes radioimmune experiments in which picogram quantities of the 16-glucosiduronate metabolites of estriol were measured in the presence of vast excesses of estriol, other estrogens and/or their metabolites. Antibody specificity together with the natural preponderance of the 16-glucosiduronate metabolites made possible their direct measurement in plasma and urine.