Radioreceptor assay for cynomolgus monkey serum luteinizing hormone

Serum luteinizing hormone (LH) of cynomolgus monkeys was measured by radioreceptor assay (RRA). The assay system consisted of 100 microliter of standard or unknown samples, 100 microliter of a receptor preparation and 100 microliter of 125I-LH (LER-960). Dispersed interstitial cells of mature rat testes were suspended in Tris-HCl buffer containing MgSO4 (5 mM), bovine serum albumin (0.1%) and sucrose (0.3 M) and used as the receptor preparation. 125I-LH was dissolved in the same buffer. The incubation was carried out at 37 degrees C for 2 to 3 hr. The nonspecific inhibitory effect of sera in the radioreceptor assay system was compensated for by using LH-free diluent prepared by heat treatment of pooled sera. Validation of the assay demonstrated good reliability in terms of accuracy, precision and sensitivity (equivalent to 3.1 micrograms LER-907/ml of serum). Recovery experiments were performed by adding known amounts of cynomolgus pituitary LH to the normal serum and mean recovery and the standard deviation of the mean was 86 +/- 13%. The intra- and inter-assay coefficients of variation were 7 and 9%, respectively. By using this RRA system, cyclic changes in serum LH during the menstrual cycle were determined in three adult female cynomolgus monkeys. These results indicate that this RRA system is useful in measuring serum LH in female cynomolgus monkeys.