AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 5 584-R594, Copyright © 1985 by American Physiological Society
Inhibition of H+ secretion by lectins in turtle bladder: role of a cell type on acidification
D. M. Potter and J. A. Arruda
Because certain lectins have been shown to bind to the intercalated cell of
the cortical collecting tubule, we investigated the effect of concanavalin
A and wheat germ agglutinin on urinary acidification in isolated turtle
bladders. After addition to the mucosal but not serosal fluid, concanavalin
A and wheat germ agglutinin decreased H+ secretion in a dose-dependent
manner, and these effects were specifically inhibited by the competitive
antagonists of concanavalin A (alpha-methyl-D-mannoside) and of wheat germ
agglutinin (N-acetylglucosamine). Concanavalin A decreased H+ secretion by
decreasing both the proton motive force and the active conductance of
protons. Although electroneutral HCO3 secretion was not inhibited by either
lectin, Na transport was decreased by 18 and 25%, respectively, after
concanavalin A and wheat germ agglutinin. Concanavalin A failed to inhibit
O2 consumption by the granular cell fraction but significantly inhibited O2
consumption by the carbonic anhydrase rich cell fraction. Morphological
studies utilizing peroxidase or fluorescein-labeled concanavalin A showed
that concanavalin A stained one cell type and that this staining was
specific since it could be blocked by the competitive antagonist
alpha-methyl-D-mannoside. Studies utilizing double labeling with
fluorescein concanavalin A and acridine orange suggested that both probes
stain the same cell type. The data strongly suggest that concanavalin A
interacts specifically with the cell responsible for H+ secretion.
