Radioimmunoassay for Bovine and Ovine Luteinizing Hormone1

Separate radioimmunoassays for bovine and ovine luteinizing hormone (LH) have been developed. Antiserum against LH was developed in rabbits and purified preparations of bovine and ovine LH were used for radioiodina-tion. Specificity of the assays was demonstrated by comparing radioimmunoassay and bioassay estimates of the LH content of pituitary preparations containing various ratios of the pituitary hormones. Using the bovine LH radioimmuno-assay and 200 μl aliquots of serum, relatively high levels (12–60 mg/ml) of LH were measured in serum from heifers on the day of estrus and measurable levels of LH were present in serum from castrated males (3–5 ng/ml). The ovine LH assay serum obtained from ewes on the day of estrus contained an average of 26 ng/ml, whereas serum obtained during the follicular and luteal phases of the cycle contained approximately 2 ng/ml. The average LH content of serum from castrated ewes was 4.9 ng/ml, whereas the level in castrated males was 20.9 ng/ml. Serum from normal male sheep contained an average of 2 ng/ml, while serum from a hypo-physectomized ewe had no detectable LH (<0.5 ng/ml). (Endocrinology84: 1166, 1969)