Use of enzyme-immunoassay for oestradiol-17β and progesterone quantification in canine serum

Abstract The objective of this investigation was to develop and evaluate competitive inhibition-enzyme-immunoassays for canine serum oestradiol-17β (E 2 ) and progesterone (P 4 ) quantification. Sera from 56 healthy bitches at various stages of oestrus cycle and pregnancy were tested. For E 2 measurement, each sample (0.4 ml) was extracted with diethyl ether and after solvent evaporation the resultant hormone was reconstituted to one-fifth of the original sample volume in aqueous buffer. Each reconstitute (30 μl) was assayed for E 2 to estimate respective serum concentration. For P 4 , each sample (10 μl) was directly assayed without extraction. The classic cyclic hormonal pattern during the oestrus cycle of the bitch was observed. The brief, sharp dominance of E 2 during the follicular phase was followed by the long-lasting dominance of P 4 during the luteal phase (late oestrus, dioestrus or pregnancy). During the anoestrus phase both hormones were found at basal levels, with the exception of E 2 during late anoestrus which appeared to be rising. Both assays had acceptable specificity (cross-reactions≤10%), precision (coefficient of variation (C.V.) 2 recovery: 97%; P 4 recovery: 104.7%). The sensitivity of E 2 and P 4 assay was 4 pg ml −1 and 0.28 ng ml −1 , respectively.