AN IMPROVED IN VITRO BIOASSAY METHOD FOR MEASURING LUTEINIZING HORMONE (LH) ACTIVITY USING MOUSE LEYDIG CELL PREPARATIONS

Abstract

ABSTRACT An improved in vitro bioassay method for the measurement of LH activity is presented. The method is based on the assay of testosterone produced by "Leydig cell" preparations from mouse testes in the presence of added gonadotrophin. The method is significantly improved in terms of sensitivity, precision and practicability when compared to the previously described bioassay method employing decapsulated testes from adult mice. The sensitivity of the improved method is 15 μIU for HCG and 50 μIU for HMG. The useful range of the method is 15–260 μIU for HCG and 50–900 μIU for HMG. Using a 3 + 3 point assay design with each dose in quadruplicate, a mean index of precision (λ̅) of 0.044 was obtained in 19 assays. Human FSH, TSH, ACTH, LTH, STH, oxytocin, vasopressin and LHRH preparations did not influence the bioassay method at levels likely to be found in biological samples. A good correlation was found between estimates obtained by the "Leydig cell" method and by the method using decapsulated testes when various HCG and HMG preparations were used. With the proposed method at least 30 samples can be assayed each week by 2 persons, with a marked reduction in cost.