Concentrations of pepsinogens A and C in peripheral blood of cattle at different developmental stages.

Measurements of global proteolytic activity of pepsinogens are successfully used for diagnosis of gastric nematode parasitism in cattle. Higher pepsinogen concentrations detected in peripheral circulation were found to be associated with damage in gastric mucosa
The aim of the present study was to investigate the ontogenesis of PgnA and PgnC in cattle. Bovine PgnA and PgnC were isolated in our laboratory. Both antigens were labeled to 125I by using chloramine T method. Standard curves ranged from 125 to 1.0 ng/mL. Antisera were raised in rabbits: AS866 (anti-PgnA) and AS869 (anti-PgnC). The optimal dilutions for primary antisera were 1:15,000 and 1:20,000 for AS866 and AS869, respectively.
In order to establish the ontogenesis of both PgnA and PgnC, samples were collected from 50 bovine fetuses (3rd to the 9th month), 18 calves and 57 adult cattle.
Mean(±SEM) concentrations of PgnA were 4.6±0.7 ng/mL, 78.9±6.7 ng/mL and 133.2±17.6 ng/mL in fetuses, calves and mature cows, respectively. Concentrations of PgnC were <0.9 ng/mL, 13.5±1.1 ng/ml and 201.5±26.5 ng/ml in fetuses, calves and mature cows, respectively. The ratio PgnA/PgnC concentrations decrease from fetal age (maximal ratio due to undetectable PgnC concentrations), being 5.8 in young calves and lowest (0.7) in mature cows.
In conclusion, PgnA and PgnC concentrations can be distinctly measured by specific RIA systems. Ratio PgnA/PgnC concentrations can be useful to better understand the ontogenesis of gastric aspartic proteinases in cattle. It is expected that clinical application of these assays will help vet practitioners to establish diagnosis of gastric nematode parasitism in dairy and beef herds taking into account the age of the animal.