Development and characterization of a homologous radioimmunoassay for equine prolactin.

This research has developed a new, specific, and sensitive assay for measuring equine prolactin levels in horse serum. The assay shows low cross-reactivity with other hormones and demonstrates high recovery of equine prolactin in serum.

Development of the Assay

• The researchers developed a homologous radioimmunoassay specifically for equine prolactin. It measures the protein’s presence in the serum of horses. This assay is a type of scientific procedure used to determine the concentration of an antigen in a solution, using the principles of antigen-antibody binding, radioactive labelling, and measuring the radioactivity of the bound antigen or antibody.

Sensitivity and Consistency of the Assay

• The sensitivity of the assay, which refers to its ability to detect the smallest amounts of equine prolactin, ranged from 0.4 to 0.6 ng/ml.
• The intra-assay and inter-assay coefficients of variation were calculated for five different doses of the hormone. The former measures the variation in measurements taken by a single person repeating the test on the same sample, whereas the latter measures the variation in averages of measurements between different people testing the same sample. For this assay, they averaged 6.9% and 15.4%, respectively, which is a relatively low level of variation, indicating consistent and reliable results.

Cross-Reactivity of the Assay

• The assay showed a low level of cross-reactivity with other mammalian and nonmammalian prolactins and growth hormones, less than 20% and 0.3%, respectively. Cross-reactivity refers to the ability of an assay to recognise and bind to substances other than the intended target, in this case, equine prolactin.
• Specifically, cross-reactivity with equine growth hormone was less than 0.07%, allowing for a specific measurement of equine prolactin without significant interference from the equine growth hormone.

Recovery and Practical Application of the Assay

• Recovery of exogenous equine prolactin in serum, essentially how much of the introduced hormone can be seen in the end result of the assay, was as high as 89%, demonstrating the high efficiency of the assay.
• The assay was initially tested on several physiological samples (e.g., from stallions, pregnant and nonpregnant mares). The prolactin values obtained ranged from 0.6 to 12.0 ng/ml, indicating the practical application and potential usefulness of this assay in research and clinical settings.