Abstract
Two-dimensional electrophoretic analysis of cattle plasma proteins was done by a 1st dimension separation in agarose gel (pH 5.0), followed by a 2nd dimension in horizontal polyacrylamide gel (pH 9.0). This method resulted in improved and reproducible separation of many .alpha.- and .beta.-globulins. Three groups of .alpha.-globulins, designated Pi-1, Pi-2 and Pi-3, inhibited the esterolytic activity of bovine trypsin and bovine chymotrypsin. Pi-2 showed appreciable inhibition only for trypsin and genetic polymorphism was observed for this protein. The hypothesis that the 3 Pi-2 types observed were controlled by 2 codominant, autosomal alleles was supported. The occurrence of a 3rd Pi-2 allele was also postulated in some animals studied. The frequency of the most common allele, Pi-2s, ranged from 0.5-0.8 in the different breeds of cattle studied (Swedish Red and White, Friesian, Jersey, Charolais and Simmental). The post-transferrins Ptf-1 and Ptf-2 in cattle plasma were 2 different genetic systems.