AJP - Gastrointestinal and Liver Physiology, Vol 240, Issue 3 211-G216, Copyright © 1981 by American Physiological Society
Effect of veratrine and 50 mM K on ileal transport and electrically induced secretion
K. A. Hubel
To obtain additional evidence that the Cl secretion caused by electrical
field stimulation (EFS) in rabbit ileum in vitro is mediated by nerves or
amine precursor uptake and decarboxylation (APUD) cells, we determined
whether the response could be prevented by agents that depolarize nerves,
veratrine or 50 mM K. EFS 1) increased transmural electrical potential
difference (PD) and the short-circuit current (Isc) and reduced total ion
conductivity (G), 2) caused Cl secretion by reducing the mucosal-to-serosal
flow of chloride (JClm leads to s) alone or in combination with an increase
in the serosal-to-mucosal flux of chloride (JCls leads to m), and 3)
reduced Na absorption or caused secretion by increasing JCls leads to m
alone or in association with a reduction in JNam leads to s. At 10(-5)
g/ml, veratrine prevented the changes in ionic fluxes caused by EFS and
reduced the PD and Isc. It did not reduce the Isc response to 5 mM
aminophylline, however. Fifty millimolar K decreased PD and Isc and
increased G. JNam leads to s and JNas leads to m diminished in proportion
to the reduction in bath Na concentration, so the net flux of sodium
(JNanet) was not affected. JClnet did not change, although both JClm leads
to s and JCls leads to m increased. Fifty millimolar K prevented the
changes in ionic fluxes caused by EFS and reduced the Isc response to
aminophylline by half. The study provides additional evidence that the
effects of EFS are mediated by nerves or electrically excitable APUD cells,
but the contribution of each is uncertain.
