Isolation and immunochemical determination of sow colostrum trypsin inhibitor

Trypsin inhibitor from sow colostrum was isolated by ion exchange chromatography on DEAE-Sephadex A-50 followed by gel filtration chromatography on Sephadex G-100 and affinity chromatography. Antiserum against sow colostrum trypsin inhibitor was produced by immunization with the purified inhibitor, and made specific by absorption with normal porcine serum. The specific antiserum was used for immunoquantitation by single radial immunodiffusion (SRI). In sow colostrum whey, good agreement was found between the results obtained by SRI and the total trypsin-inhibiting activity as determined by radial diffusion in a casein-containing agarose gel (r = 0.97, n = 10). In sow's milk there was only a very low inhibiting activity, and no colostral inhibitor was demonstrable by SRI. Also in baby-pig urine agreement was found between the two methods (r = 0.97, n = 14). In baby-pig serum such an agreement was not seen, undoubtedly becuase of the presence of genuine serum trypsin inhibitors. By the SRI technique it is possible specifically to determine the colostral inhibitor even in the presence of other trypsin inhibitors.