Serum isoamylases in cystic fibrosis

Salivary and pancreatic isoamylases were determined in the sera of 33 patients with cystic fibrosis (CF) and in 34 CF-parents. Pancreatic serum isoamylase activities were greatly decreased in patients with CF, and only two values from this group fell within the normal range. Salvary isoamylases, however, were markedly increased so that the total serum amylase activities were normal. We interpret the low pancreatic isoamylase levels in serum to reflect reduced exocrine masses in the pancreas of CF-children. In heterozygotes, the mean activity of the pancreatic isoamylase was significantly higher than in the reference group, while salivary isoamylases were within the normal range. Due to a genetic polymorphism pancreatic isoamylase may occur in two main fractions. This variant type of pancreatic isoamylase appeared more frequently in CF-heterozygotes than was expected from a reference group of blood donors.