Effect of two virus inactivation methods: electron beam irradiation and binary ethylenimine treatment on determination of reproductive hormones in equine plasma.

Ionizing irradiation and binary ethylenimine treatment have previously been shown to be effective for in-vitro inactivation of virus in biological material. In the present study the 2 methods were tested for possible effects on measurable concentrations of reproductive hormones in equine plasma (luteinizing hormone (LH), folliclestimulating hormone (FSH), progesterone (P4), and oestradiol-17 beta (E2)). The inactivation methods were electron beam irradiation with a dose from 11 to 44 kGy or treatment with binary ethylenimine (BEI) in concentrations of 1 and 5 mmol/L. Generally, there was a close correlation (r > 0.8, < 0.001) between pre- and post-treatment hormone levels. Thus, the different phases of the oestrous cycle could be distinguished on the basis of measured hormone concentrations of treated samples. However, both treatments significantly changed hormone concentrations of the plasma samples. For LH, FSH, and E2 the effect of irradiation and BEI treatment was depressive and dose-dependent. For P4 the effect of irradiation was also depressive and dose-dependent. However, the highest dose of BEI resulted in an increase of measured P4 concentration, which may be attributed to changes in the plasma matrix due to the treatment. Although the treatments affected measured hormone concentrations, the close correlation between pre-treatment and post-treatment measurements means that the diagnostic value will remain unchanged.