SOURCES OF ERROR IN CLINICAL BIOASSAYS OF SERUM CHORIONIC GONADOTROPIN

Abstract

The biological activity of human chorionic gonadotropin (HCG) dissolved in serum or plasma was compared with that of HCG dissolved in saline using a variety of bioassay methods in intact and hypophysectomised rats. Assays were conducted in 2 independent laboratories. The effect of HCG on the various accessory reproductive organs of intact or hypophysectomised immature male rats was not increased significantly when the hormone is dissolved in serum or plasma instead of saline. Accordingly clinical bioassays of HCG in untreated serum or plasma are valid if the prostatic weight, seminal vesicle weight, or the weight of the total accessory reproductive organs are used as indices of response. Under the experimental conditions used the effect of HCG on the uterine weight test in rats was increased approximately 2-fold when the hormone was dissolved in serum or plasma instead of saline. This method is not suitable for the assay of HCG in untreated serum or plasma. Assays depending on the ovarian weight test were so inaccurate that it was not possible to assess whether plasma had any significant effect in increasing or decreasing the biological activity of HCG.