[Simple and rapid heterologous method of radioimmunochemical determination of luteinizing hormone in the blood serum of rats. 2. Specificity of the method].

The Heterologous hard phase radioimmunochemical method (RICM) of luteinizing hormone (LH) determination was tested in a number of experimental models for specificity. The results obtained demonstrated that a possible factor of cross reaction with the thyrotropic hormone (TTH) and the folliculo-stimulating hormone (FSH) was apparently insignificant in determination of LH in rat serum. This conclusion was based on the following. An immunosorbent used in RICM, prepared from the antisera of rabbits immunized with sheep LH, failed to interact with the FSH of rat hypophysis extracts. TTH-releasing hormone failed to alter the level of the immunoreactive LH in rat serum, whereas LH-releasing hormone increased 31-fold the LH concentration in 20 min. Besides, by means of RICM there was recorded a marked increase of the LH in the serum of rats after ovariectomy and a fall of the LH concentration in response to the administration of estradiol together with progesteron to such rats.