Studies on porcine pancreatic elastase activity. I. Radioimmunoassay of porcine pancreatic elastase.

An improved method of radioimmunoassay was devised to offer a successful formula for determining blood concentration of elastase. With porcine pancreatic elastase as the antigen, rabbits were immunized to obtain antiserum. Iodinated elastase labeled by the chloramine-T procedure using 131I (or 125I) had a specific activity of 200-300 mCi/mg. The double antibody method was used for BF separation. While the usual method of radioimmunoassay was not always successful in obtaining accurate serum concentration of elastase, the use of diisopropyl fluorophosphate (DFP) was able to eliminate the disturbing influence of intra-serious inhibitors, alpha 1-AT and alpha 2-M, eventually producing satisfactory results. With the use of DFP, the elastase standard curve and the porcine serum dilution curve had a statistically significant correlation; precision and recovery were both satisfactory; cross-reactivity of the antiserum with trypsin and chymotrypsin was less than 0.001%. The minimal detectable concentration of elastase was 5 ng/ml, and the range of normal fasting porcine serum level was 70-100 ng/ml.