Journal of Applied Physiology, Vol 50, Issue 2 383-391, Copyright © 1981 by American Physiological Society
Kinetics of sulfated mucous glycoprotein secretion in dog trachea in vitro
J. A. Estep, J. P. Zorn and M. G. Marin
Previous studies on mucous glycoprotein secretion in respiratory epithelium
most often provided qualitative, rather than quantitative, data. This study
describes a new technique to measure the secretion rate, pool size, and
turnover time of the pool of sulfated mucous glycoproteins of dog tracheal
epithelium. The technique involved interposing dissected tracheal
epithelium between the halves of an Ussing-type chamber, incubating the
submucosal side of the tissue with 35SO4, and measuring the rate of
appearance of nondialyzable 35SO4 on the luminal side of the chamber of
both during the labeling and "washout" of the mucous pool. By analyzing the
pattern of elimination, we showed that 1) a steady secretion rate of
labeled mucous glycoprotein occurs within 3-4 h when free 35 SO4 is present
on te submucosal side of the tissue, 2) secretion is consistent with
first-order kinetics from a single pool, 3) puromycin decreases the rate of
secretion of labeled mucous glycoprotein, 4) secretion rate is greater in
medium 199 than in modified Krebs-Henseleit solution, and 5) 1.2 mM SO4
supports maximal baseline secretion. In six tracheas, bathed in
Krebs-Henseleit solution, the secretion rate was (mean +/- SE) 467 +/- 74
pmol SO4 x cm-2 x h-1, pool size, 964 +/- 144 pmol SO4/cm2, and turnover
time, 2.12 +/- 0.16 h. This technique provides a quantitative method to
characterize kinetics of sulfated mucous glycoprotein secretion.
