Heterologous radioimmunoassay of fox LH: Levels during the reproductive season and the anoestrus of the red fox ( Vulpes vulpes L.)

A heterologous radioimmunoassay using ovine LH as the labeled hormone, canine LH as the standard, and an antiovine LH rabbit serum was validated for the measurement of fox LH. Physiological validation of the assay was evidenced by the high concentrations of LH at oestrus and following ovariectomy or the administration of LH-RH. Throughout the year, plasma LH levels demonstrate important variations, being low during and after the luteal phase (1.4 ± 0.3 ng/ml) (mean ± SE) and increasing during the second part of anoestrus (5.2 ± 1.4 ng/ml). This latter increase might be correlated with that of androgens observed at the same period. Several LH rises preceded the preovulatory LH surge.