A SENSITIVE IN VITRO BIOASSAY METHOD FOR LUTEINIZING HORMONE (LH) ACTIVITY

Abstract

ABSTRACT A specific and sensitive in vitro bioassay method is described for the measurement of LH activity of HCG, HMG and human hypophyseal gonadotrophin (HHG) preparations. The method is based on the principle that a linear relationship exists between graded doses of HCG, HMG or HHG preparations and the amount of testosterone released into the incubation medium by decapsulated mouse testes. The sensitivity of the method is 0.4 mIU/ml incubation medium for HCG and 2 mIU/ml for HMG. The useful range of the method is 0.4– mIU/ml for HCG and 2–32 mIU/ml for HMG preparations. A 3 + 3 point design with 6 individual observations per dose is used. Under these experimental conditions the mean index of precision (γ) in 44 assays was 0.22. All HCG, HMG and HHG preparations yielded parallel dose-effect lines. In the concentrations studied, the assay was not influenced by the presence of FSH, ACTH, STH, LTH, vasopressin, oxytocin and LH releasing hormone activities. The high LH contamination of the highly purified TSH preparations studied precluded an adequate assessment of a possible synergistic or antagonistic effect of TSH on the assay.