Effect of plasma interference on different vasopressin antisera.

The effect of plasma interference upon 2 AVP antisera both of high affinity and specificity, was investigated. Chromatography of plasma from a normal subject on Sephadex G-25 gave 3 peaks of AVP-like material with antibody A eluting in the void volume, salt volume and in the AVP volume; the quantity of AVP-like material detected in the void volume was 95% less with antibody B. Similar elution profiles were observed in a patient with cranial diabetes insipidus but the third peak was absent. AVP-like material in the first 2 peaks was probably due to interference in the radioimmunoassay. Extraction of plasma by Florisil reduced the first 2 peaks (antibody A) and eliminated the void volume peak (antibody B). Plasma interference affected the absolute values of plasma AVP concentrations of osmotically-stimulated normal and diabetic subjects. AVP antisera displaying least plasma interference are recommended for AVP radioimmunoassay.