[Specificity and precision of a radioimmunoassay of dihydroergotoxine in plasma].

For the quantitative and qualitative determination of dihydroergotoxine methanesulphonate (DCCK) a radioimmunoassay was developed. This method involves use of an antibody against the dihydrolysergic acid moiety and an 125I-labelled dihydrolysergic tracer. The differentiation of dihydroergopeptides, lysergic acid and the ergopeptides was obtained by modification of extraction methods already published. The assay procedure detects around 10 pg/ml dihydroergotoxine. Dihydrolysergic acid and lysergic acid are not detectable up to about 6 ng/ml. Ergometrine and alpha-ergocryptine show cross-reactivities of 14% and 7.5%, respectively. All dihydroergopeptides included in dihydroergotoxine show the same cross-reactivity as dihydroergotoxine itself. Intra- and inter-assay variations were approximately 12% and 13%, respectively.