Rapid detection of the preovulatory luteinizing hormone peak in the blue fox (Alopex lagopus) by an enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) developed for the rapid measurement of luteinizing hormone (LH) in blood of many mammalian species has been validated in the fox. For this purpose, daily plasma samples collected from six vixens during the periovulatory period were assayed for LH using ELISA. The results were compared with those obtained by radioimmunoassay (RIA), and related to parameters used to determine the time of ovulation (onset of oestrus, vaginal electrical resistance peak) and to ovarian findings. This ELISA provided a highly sensitive measure of LH (125 pg ml-1) from a 10 microliters plasma sample within 3 h. Plasma concentrations of LH measured by ELISA and RIA were significantly correlated (r = 0.911). In the blue fox, ovulation occurs once a year and coincides with the start of oestrus. The LH peak preceded the start of oestrus by 1.5 days (1-3) and preceded the vaginal electrical resistance peak by 2.2 days (1-4). The rapid and precise detection of the preovulatory LH peak by this assay provides a convenient method to determine the time of ovulation and therefore the optimum time for artificial insemination or oocyte collection for fertilization in vitro.