Methylumbelliferyl-guanidinobenzoate reactive proteases in amniotic fluid: possible marker for cystic fibrosis [letter].

Previous studies in our laboratory have demonstrated significant differences in the extent 
of protease reactivity with MUGB (4-methylumbelliferyl guanidinobenzoate, a sensitive active site 
titrant of many serine proteases) when plasma and cultivated skin fibroblasts 
from patients with cystic fibrosis (CF), obligate heterozygotes, and controls were 
compared. Because of these observations, and the potential value of amniotic 
fluid for the prenatal detection of cystic fibrosis, these studies were 
extended to human amniotic fluid obtained by amniocentesis done for the 
intrauterine detection of genetic and other fetal abnormalities. An amniotic-fluid sample 
obtained from a woman who was subsequently delivered of a baby 
with CF showed a much reduced level of MUGB reactivity similar 
to the relative deficiency observed in plasma and cultivated skin fibroblasts 
from patients with CF. These observations suggest that amniotic-fluid protease activity 
may be a useful marker for the prenatal detection of CF. 
