International Collaborative Study by in vitroBioassays and Immunoassays of the First International Standard for Inhibin, Human Recombinant

Abstract

Abstract.The First International Standard for Inhibin, Human Recombinant, (ISI), a lyophilized preparation of rDNA—derived human 32 kDa Inhibin A in ampoules coded 91/624, was evaluated by international collaborative study for its suitability to serve as an International Standard. This study, which involved 15 laboratories in nine countries, included a variety of in vitrobioassays and immunoassays. The ISI was compared with two other lyophilized preparations of human recombinant inhibin, the International Standard for Porcine Inhibin (ISP) and preparations of human follicular fluid inhibin. Predicted loss of activity based on estimates of potency of contents of ampoules which had been stored under conditions of accelerated thermal degradation indicated that the ISI has satisfactory stability. On the basis of the results of this study, the ISI was deemed suitable to serve as a standard for in vitrobioassays and immunoassays and was established by the Expert Committee on Biological Standardization of the World Health Organization as the First International Standard for Inhibin, recombinant human, with an assigned unitage of 150 000 International Units per ampoule. This unitage maintains an approximate continuity of units with the ISP.