AJP - Gastrointestinal and Liver Physiology, Vol 241, Issue 5 443-G450, Copyright © 1981 by American Physiological Society
Intestinal secretion of mucin in chronically reserpine-treated rats
J. Forstner, B. Maxwell and N. Roomi
Intestinal glycoprotein synthesis and secretion were measured in vivo and
in vitro in rats treated for 7 days with reserpine. Goblet cell mucin was
measured by radioimmunoassay. Reserpine-treated rats contained 1.4 times
more mucin in intestinal tissue than control rats (P less than 0.05) and
incorporated [1-14C]glucosamine in vivo at 1.52 times the rate of controls
(P less than 0.01). Intestinal slices incubated for 90 min in vivo
incorporated 1.4 times more [14C]glucosamine (P less than 0.001) and 3.0
times more [3H]threonine (P less than 0.01) into protein of
reserpine-treated tissue than controls. The extra 14C was localized to
mucin and to smaller components that had affinity for
Concanavalin-A-Sepharose, did not bind to mucin antibody, and were
therefore nonmucin glycopeptides. In vitro secretion of mucin was three
times greater for reserpine-treated tissue than for control tissue (P less
than 0.0001). There was an impairment in the mucin secretory response of
reserpine-treated tissue to the addition of cholera toxin. Thus, chronic
reserpine treatment results primarily in a generalized increase in the rate
of intestinal glycoprotein synthesis, subsequent accumulation in tissues,
and an increased (but not fully proportional) secretion of mucin. We
speculate that in cystic fibrosis a similar sequence of glycoprotein
abnormalities may be responsible for the gradual obliteration of exocrine
gland ducts with viscous mucus.
