Quantitative changes in a serum protein, AS, during the life cycle of the lamprey,Petromyzon marinus L

The electrophoretically fastest migrating protein in ammocoete serum, AS protein, was isolated and found to be an acidic glycoprotein with a molecular weight of 140,000 Daltons. Purified AS was injected into rabbits to produce a monospecific antiserum that was used in rocket immunoelectrophoresis to quantitate AS at different periods in the life cycle. AS was found to constitute approximately 70% of total serum protein in the ammocoete, remained at about the same value during transformation, and was reduced to 38% of total serum protein in the juvenile adult. In both male and female upstream migrant animals, AS was less than 0.5% of total serum protein. When juveniles were acclimated to seawater over a 10 week period, it was found that their AS level was reduced by 92% to 3.8% of total serum protein. These results are discussed in relation to changes in other serum proteins at various intervals of the lamprey life cycle.