Journal of Applied Physiology, Vol 67, Issue 1 276-281, Copyright © 1989 by American Physiological Society
Transepithelial prostacyclin gradient in isolated canine trachea
D. H. Eidelman, W. S. Powell, S. Bellofiore and J. G. Martin
Meakins-Christie Laboratories, McGill University, Montreal, Quebec, Canada.
Cyclooxygenase products of arachidonic acid, potential modulators of airway
smooth muscle, have recently been described in bronchoalveolar lavage from
canine lungs. To evaluate the possibility that airway epithelium represents
a barrier to movement of prostacyclin (PGI2), an important bronchodilator
synthesized by isolated airway, we measured the concentrations of
6-oxoprostaglandin F1 alpha (6-oxo-PGF1 alpha), the stable degradation
product of PGI2, on the mucosal and serosal sides of isolated canine
tracheal segments (CTS) mounted in Ussing chambers. 6-oxo-PGF1 alpha was
measured by radioimmunoassay after purification by high-performance liquid
chromatography. The concentration of 6-oxo-PGF1 alpha was significantly
higher on the serosal than the mucosal side of CTS (1,262 +/- 252 vs. 390
+/- 168 pg.min-1.g-1, n = 8, P less than 0.05). A significant correlation
was present between 6-oxo-PGF1 alpha measured on both sides of each CTS (r
= 0.778, n = 26, P less than 0.01). 6-oxo-PGF1 alpha production from CTS
stripped of mucosa was significantly greater than from isolated mucosa.
Radiochromatograms obtained after incubation with [3H]arachidonic acid and
calcium ionophore A23187 confirmed PGI2 as the predominant cyclooxygenase
product of the submucosa, whereas the mucosa produced only small amounts of
PGI2 in proportion to other cyclooxygenase products. PGI2 (10(-8) to 10(-6)
M) applied to the mucosal surface of closed tracheal segments precontracted
with histamine resulted in no significant relaxation, whereas serosal
application showed a concentration-dependent effect. Radiolabeled
6-oxo-PGF1 alpha did not cross the isolated epithelium.(ABSTRACT TRUNCATED
AT 250 WORDS)
