Development of a Radioimmunoassay for Bovine Pepsinogen A

Pepsinogen A is the most abundant zymogen found in blood, and its enzymatic measurement is used for the diagnosis of gastric lesions. The present study was conducted to develop a radioimmunoassay (RIA) specific to pepsinogen A in bovine plasma. The authors purified large amounts of three non-denatured isoforms of bovine pepsinogen A with high proteolytic activity. These homogeneous preparations were used to produce specific antisera in New Zealand White rabbits, and three antisera with high titers were obtained. In the present assay the antiserum #822 was used at a final dilution of 1/250,000. The detection limit of the assay was 20 ng/ml and the recovery ranged from 85.5 to 103.3%. The repeatability (intra-assay coefficient of variation) was lower than 6.6%, whereas the reproducibility (inter-assay coefficient of variation) was lower than 13.4%. The capacity of the RIA to detect pepsinogen A in blood was tested by measuring the concentrations in plasma of newborn calves (n = 6) serially sampled from birth to four months of age. The mean pepsinogen A value (mean ± standard deviation) in the plasma of calves was 2071 ± 752 ng/ml one day after birth. The concentration decreased progressively and was about 1196 ± 307 ng/ml at day 21, and 677 ± 109 ng/ml at day 120. The present study is the first report on pepsinogen A concentrations in bovine measured by RIA. Further investigations using the RIA should be performed in order to confirm these values and determine pepsinogen levels in older cattle in physiological and pathological conditions such as gastrointestinal helminthosis.