Am. J. Respir. Cell Mol. Biol., Vol 11, No. 3, Sep 1994, 321-328.
Chymotryptic activity in perfusates of isolated rat trachea: correlation with mucosal and connective tissue mast cell secretion
EK Tam, J Aufderheide and XY Hua
Department of Medicine, University of California.
Serine proteinases participate in many inflammatory events in the airway.
We therefore screened perfusates of isolated rat tracheas for tryptic,
elastolytic, and chymotryptic serine proteinases. Only chymotryptic
activity, indicated by hydrolysis of the synthetic substrate
N-succinylalanylalanylprolylphenylalanyl p-nitroaniline (AAPF), was
consistently detected in these perfusates. Basal levels of chymotryptic
activity were not increased significantly by electrical field stimulation
(EFS) (mean change +/- SEM: -0.05 +/- 0.05 m o.d. units, n = 4) or by
10(-7) M substance P (SP) (+0.04 +/- 0.02 m o.d. units, n = 14). However,
the mean change after the stimuli were jointly administered (0.17 +/- 0.06
m o.d. units, n = 12) was significantly greater than control or after EFS
(P = 0.01, one-way ANOVA). The SP + EFS-induced chymotryptic activity was
inhibited by PMSF, soybean trypsin inhibitor, and chymostatin and was
associated with an increase in histamine concentration and immunoreactivity
to rat mast cell proteases (RMCP), indicating that the activity is due to
mast cell degranulation. However, the activity was not significantly
decreased by pretreating rats with systemic compound 48/80. SP +
EFS-induced chymotryptic activity peaked rapidly and was associated with
modest histamine release and an immediate peak in immunoreactivity to RMCP
II, a marker of mucosal mast cells. Immunoreactivity to RMCP I, a marker of
connective tissue mast cells, also increased after SP + EFS, but this
immunoreactivity was either delayed or more sustained and did not coincide
with the peak of chymotryptic activity.(ABSTRACT TRUNCATED AT 250 WORDS)
