Journal of Applied Physiology, Vol 72, Issue 2 608-611, Copyright © 1992 by American Physiological Society
Viral infection increases contractile but not secretory responses to substance P in ferret trachea
T. C. Murray and D. B. Jacoby
Division of Pulmonary and Critical Care Medicine, University of Maryland, Baltimore 21201.
Viral infection increases the airway smooth muscle response to substance P.
This effect is due to decreased activity of neutral endopeptidase (EC
3.4.24.11), an enzyme that degrades substance P. Inhibition of neutral
endopeptidase activity also potentiates substance P-induced 35SO4-labeled
macromolecule secretion. Therefore we examined the in vitro effects of
substance P on 35SO4-macromolecule secretion from the tracheae of
influenza-infected ferrets. Despite a virus-induced loss of neutral
endopeptidase activity (demonstrated in muscle bath experiments), there was
no difference between control and infected tracheae in either baseline
secretion [697 +/- 125 vs. 579 +/- 67 (SE) cpm/15 min; n = 15 tissues) or
in the response to 10(-6) M substance P (increased by 218 +/- 63 and 195
+/- 51, respectively) or 10(-5) M substance P (increased by 416 +/- 95 and
354 +/- 54, respectively). Although phosphoramidon (10(-6) M) potentiated
the secretory response to substance P, there was again no difference
between control and infected tracheae. These data show that although viral
infection decreases airway neutral endopeptidase activity, virus-induced
hypersecretion is not due to a resulting increase in the secretory response
to substance P.
