Radioimmunoassay for PMSG and its application to in-vivo studies.

This research study shares the development of a radioimmunoassay for PMSG detection in cattle blood, after external application, and the results of the experiment. The assay technique was able to effectively measure PMSG, while eliminating any influence from other hormones and substances, providing a reliably high recovery mean with minimum deviation. The PMSG detected in pregnant mares’ blood was comparable to findings from a bioassay, and signals of PMSG could still be detected 10 days after injection.

Radioimmunoassay Development

• The researchers developed a double-antibody radioimmunoassay, specifically to measure PMSG, a hormone, in the blood of cattle after it has been applied externally.
• They used a rabbit antiserum against PMSG and pure PMSG for radioiodination.
• There was a strong cross-reaction with equine LH and FSH, two other hormones. However, minimal cross-reaction with bovine LH and FSH could be removed by including bovine LH in every assay tube.

Calculation and Measurement Accuracy

• Any unspecific and interfering influences from equine or cow serum were removed by adding a constant amount of PMSG-free serum to each tube.
• This method allowed for the recovery of PMSG added to 200 microliters of serum at a mean of 90.5% with a deviation of 9.9%.
• The coefficient of variation within the assay was 6.9%, and between assays was 12.6%, showing good consistency and precision of the assay.
• The sensitivity of the assay was recorded as 1 mi.u. PMSG/tube.

Application to In-Vivo Studies

• The researchers found that PMSG measurements taken in the serum of pregnant mares using this assay were comparable to those obtained from a bioassay on the same samples.
• PMSG was still noticeable in the blood serum about 10 days after an injection of 1500-3000 international units of PMSG.
• After infusing two heifers with 12,000 international units of PMSG for three hours, the half-life of PMSG was discovered to have two components: one of 51 or 40 hours and another, slower one of 123 or 118 hours.