AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 5 688-G694, Copyright © 1986 by American Physiological Society
Effects of taurine-conjugated bile salts on ionic transport of the rabbit esophageal mucosa
J. L. Goldstein, L. N. Schmidt, F. J. Al-Bazzaz and T. J. Layden
Bile salts have been implicated as a cause of esophageal injury. We
examined in vitro the changes in ionic transport of the rabbit esophagus
resulting from taurine-conjugated bile salts at neutral pH to define and
characterize their actions independent of hydrogen ion. In an Ussing
chamber changes in potential difference (PD, mV), short-circuit current
(SCC, microA X cm-2) and resistance (R, omega X cm2) resulting from
taurocholate (TC), taurodeoxycholate (TDC) and taurochenodeoxycholate
(TCDC) were studied. Transport properties were unaffected by TC at 5 and 10
mM. With TDC (5 mM) there was an initial rise in SCC and PD. After 60 min
PD and R declined in association with an increase in paracellular
permeability as measured by [14C]sucrose flux. TCDC (5.0 and 7.5 mM) caused
a sustained rise in PD and SCC with a greater rise seen at 7.5 mM. The rise
in SCC after TCDC was secondary to an increase in net sodium absorption as
basal net sodium absorption increased threefold from 0.15 +/- 0.03 to 0.44
+/- 0.10 mu eq X cm-2 X h-1. Increased net sodium absorption accounted for
73% of the TCDC-induced rise in SCC. Amiloride (10(-4) M) added to the
mucosal solution significantly inhibited this bile salt-induced rise in
SCC. We conclude that bile salts alter ionic transport in the esophageal
mucosa independent of hydrogen ion. These changes are characterized by an
early selective increase in apical membrane cation conductance and with
longer exposure, particularly in the presence of more hydrophobic bile
salts, there is a marked increase in paracellular conductance.
