Plasma arginine esterase activity in cystic fibrosis of the pancreas.

Using a micro-method for the determination of plasma arginine esterase activity, we have investigated the values for soybean trypsin inhibitor (STI)-inhibited arginine esterase activity in patients with cystic fibrosis, obligate heterozygotes and age matched control individuals. The mean of STI-inhibited activity is lowest for cystic fibrosis patients while the mean for normal controls is the highest. The mean of STI-inhibited activity for the heterozygotes is midway between the values of the patients and the normal individuals. The deficiency of arginine esterase activity was statistically significant for both cystic fibrosis patients and heterozygotes.