A sensitive microtitre plate enzyme immunoassay of oestradiol-17 beta in the cow and mare.

This study presents a sensitive method for measuring levels of oestradiol-17 beta, a form of estrogen, in cows and horses using a specialized immunoassay on microtitre plates with enzyme conjugates.

Methodology

• The researchers began by coating microtitre plates with an antiserum which was obtained from sheep’s blood. The antiserum was specific to oestradiol-17 beta attached to bovine serum albumin, providing specificity to the assay.
• Peroxide-free diethyl ether, prepared daily with treatment from Al2O3, was used to extract plasma samples. This step ensured that the oestradiol-17 beta in samples could be effectively analyzed.
• An enzyme conjugate was prepared to help detect the oestradiol. This conjugate was created by coupling oestradiol-17 beta to horse-radish peroxidase, an enzyme that would enable the measurement of the hormone’s presence.

Standard Curve and Assay Proceedings

• The conjugate was then chromatographed on a Sephadex G-25 column, which further facilitated the detection process. This created a standard curve that ranged from 0.37 to 18.40 fmol/well of oestradiol-17 beta, establishing a range for comparison with the samples being tested.
• The amount of oestradiol-17 beta that caused a 50% reduction in maximum binding was 4.4 fmol/well, which provided a reference point for the study.
• Standards and samples were incubated overnight at 4 degrees Celsius, after which the conjugate solution was added and further incubation was carried out for another 2 hours at the same temperature.
• Tetramethylbenzidine served as a chromogen, enabling visible detection of the reaction’s end product. The optical density of each reaction was measured at 450 nm to correlate with the amount of oestradiol-17 beta present.

Results

• The patterns of oestradiol-17 beta throughout a normal oestrus cycle in cows and mares were presented, showcasing the expected levels of this hormone in standard conditions.

Conclusion

• The research established a reliable, sensitive method for measuring the presence and quantity of oestradiol-17 beta in cows and horses, which can be useful in clinical and research contexts related to reproductive health in these animals.