Postcoital luteinizing hormone release in male and female rabbits as determined by radioimmunoassay.

We have developed a homologous radioimmunoassay for rabbit luteinizing hormone (LH), which was used to measure LH levels in sera of male and female rabbits before and after copulation. The results demonstrated the following: (1) LH concentrations in male and estrogen-primed female rabbits are similar prior to coitus; (2) following coitus, LH levels rise within 3 minutes in both sexes and reach a peak or plateau within 15 minutes; (3) elevated LH concentrations are maintained at a plateau for at least 1 hour in females and then fall toward base line values; (4) an increase in serum LH to 300 ng/ml (10- to 11-fold) or greater is sufficient to cause ovulation and the formation of corpora lutea; and (5) the postcoital rise in LH levels is greater in estrogen-primed females than in nontreated males.