Blockade of LH-RH induced ovulation in immature rats by LH-RH antiserum.

An in vivo method for the determination of the biological potency of luteinizing hormone-releasing hormone (LH-RH) antiserum is described. Antiserum blockade of LH-RH-induced ovulation was shown in immature rats primed with pregnant mares antiserum. A modified methods of induction of LH-RH antibodies in rabbits is described. Subjects for antibody induction were 3 mature New Zealand white rabbits. They were injected in the foot pads with 1 ml of LH-RH adjuvant solution once a week for 6 weeks. 39 days after the initial inoculation each rabbit was injected iv with 1 mg of LH-RH in .1% gelatin in physiological saline. Beginning 7 weeks after the initial inoculation 50 ml of blood was withdrawn by cardiac puncture. 5 days before each subsequent bleeding the iv injection was repeated. Animals were bled at 6-week intervals. Complement was inactivated by incubating sera in a water bath at 56 degrees C for 20 minutes. Sera were then frozen lypholized and stored at -20 degrees C. LH-RH antibodies were produced in 2 of the 3 animals so immunized. Equine serum gonadotropin (PMS) was injected in rats on Day 24. On Day 26 different doses of LH-RH antiserum or normal rabbit serum were given followed by an ovulatory dose of LH-RH. Rats were killed on Day 27. PMS or LH-RH alone did not cause ovulation. In PMS-primed rats 250 ng of LH-RH induced ovulation in all rats tested. Smaller doses had produced ovulation in some. At 100 and 300 micro 1 of LH-RH antiserum ovulation was blocked in 50 and 100% of rats respectively. This method of passive immunization is considered to be better than other in vivo assays of LH-RH antibodies.