Serum LH Levels in Bulls Treated with Synthetic Luteinizing Hormone-Releasing Hormone/Follicle Stimulating Hormone-Releasing Hormone (LH-RH/FSH-RH)2

Abstract

PRIOR to commencing studies to evaluate concentrations of bovine serum LH in response to synthetic LH-RH/FSH-RH, a double antibody radioimmunoassay was developed and validated for bovine LH. Synthetic LH-RH/FSH-RH (0.03, 0.3 and 3.0 µg/kilogram) was injected intramuscularly into each of four Hereford bulls to determine concentration of serum LH in response to this decapeptide. The sequence of treatments was initially determined at random with each bull receiving a different treatment at any one injection period. Each bull received each dose at 9-day intervals. The 0.03 µg/kilogram treatment did not induce a significant increase in mean peak serum LH concentration (2.7±0.4 ng/ml) relative to the highest serum LH concentration in the saline treated controls (1.9±0.4 ng/ml), but both the 0.3 and 3.0 µg/kilogram doses significantly increased mean peak serum LH concentrations to 14.8±2.1 and 46.2±7.0 ng/ml, respectively. The duration of the elevation in serum LH after injections of LH-RH/FSH-RH was 55±15, 220±12 and 366±33 min. for the 0.03, 0.3 and 3.0 µg/kilogram doses, respectively. Subcutaneous placement of 1.3 µg LH-RH/FSH-RH per kilogram body weight in either acidified saline, 2% carboxymethylcellulose or a silastic implant elicited a peak serum LH response of 41±10, 55±10 and 4±4 ng/ml, respectively. The duration of LH response was significantly longer for LH-RH/FSH-RH in CMC than for LH-RH/FSH-RH in acidified saline (60±92 vs. 285±40 min., respectively). The subcutaneous LH-RH/FSH-RH silastic implants failed to elicit a significant LH response. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science.