INTERNATIONAL COLLABORATIVE CALIBRATION OF A PREPARATION OF EQUINE CHORIONIC-GONADOTROPIN (ECG NZY-01) PROPOSED AS A NEW STANDARD

A batch of partially purified equine chorionic gonadotrophin (eCG NZY- 01) was freeze-dried in vials of 500 iu and characterized in a large n umber of in vivo and in vitro assays. These assays were performed in e ight laboratories in seven countries (Argentina, Belgium, England, Fra nce, Germany, Holland and USA). Four of these laboratories were in uni versities or government research organizations and four were those of pharmaceutical companies. Good correlation between in vivo and in vitr o assays was found for unknown samples and for commercial preparations from different sources when performed against eCG NZY-01 as the stand ard. This result suggests that, in contrast to the WHO IRP2 internatio nal standard, the eCG NZY-01 preparation contains all eCG isoforms in proportions roughly similar to those found in serum and commercial pre parations. The consistency of the data when using eCG NZY-01 as the re ference in all types of in vivo and in vitro assays validates the wide use of in vitro assays which are cheaper, quicker and ethically prefe rable to in viva assays. Vials of 500 iu eCG NZY-01 are available to r esearchers and manufacturers.