Equine Chorionic Gonadotropin (eCG) previously known as Pregnant Mare Serum Gonadotropin (PMSG) has been used for decades in regulating reproduction in various domestic animal species. Its use necessitates a good measurement of its bioactivity in commercial preparations. The EUROPEAN PHARMACOPEIA (EP 7.0) recommends 5-6 subcutaneous injections in immature female rats for the in vivo bioassay for eCG as in the case for measurement of FSH bioactivity in the Steelman & Pohley assay (1953). This recommendation is in marked contrast with the classical and long-time used PMSG assay of Cole & Erway (1941) that includes only one subcutaneous injection, 3 days before measurement of ovarian weight. As this difference introduces much confusion in the determination of eCG/PMSG bioactivity in commercial sources, we have performed parallel assays of several PMSG preparations, with both protocols. The single-injection protocol takes into account the long half-life of eCG in bloodstream and provokes an ovarian stimulation at lower concentrations than the multiple-injection protocol. As the single-injection protocol also mimicks the protocol used in cattle, it is preferable to the multiple-injection protocol of the current EP.
Keywords: Gonadotropin; In vivo assay; PMSG; Pharmacopea; Protocol; eCG.
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