COMPARISON OF DIFFERENT PROGESTAGEN ASSAYS FOR MEASURING PROGESTERONEMETABOLITES IN FECES OF THE BITCH

From 12 bitches of various breeds with fertile oestrus cycles faecal s amples were collected daily from the onset of pro-oestrus till 20 days after the start of vulval bleeding, then once per week till about 1 w eek before term. Immunoreactive progesterone metabolites were extracte d from the samples using methanol and measured using immunoassays. In a first experiment four different assays were compared in regard to th e amounts of immunoreactive substances measured: the enzyme immunoassa y against 20-oxo-3-hydroxypregnanes showed twice to four times higher values of immunoreactive material than another using an antibody again st 6 beta-hydroxyprogesterone. An enzyme immunoassay for pregnanediol measured only low concentrations of immunoreactive material. Also a ra dio immunoassay using an antibody against 11 beta-hydroxyprogesterone detected only small amounts of reacting material. High performance liq uid chromatography showed that in faeces of bitches the immunoreactive progesterone metabolites were present in unconjugated form, mainly as 3 alpha/beta hydroxylated progestagens with a 20-oxo group. In the se cond experiment the samples were measured with the assay system using the 20-oxo-3-hydroxypregnane antibody. A few days before mating the co ncentration of progesterone metabolites increased, reaching 5.77 mu mo l/kg faeces (median) at the day of mating. High levels (10.45 mu mol/k g faeces) were measured till the end of the first month after mating. Thereafter, the concentrations decreased, reaching 2.68 mu mol/kg (med ian) at the end of the second month.