AJP - Regulatory, Integrative and Comparative Physiology, Vol 239, Issue 5 445-R449, Copyright © 1980 by American Physiological Society
Membrane potentials and chloride activities in epithelial cells of Aplysia intestine
G. A. Gerencser and J. F. White
Microelectrodes were used to measure the potential difference across the
mucosal membrane (psi m) of cells lining the mucosa of isolated Aplysia
californica intestine. In glucose-free sodium chloride seawater medium psi
m was -68.2 +/- 2.2 mV, the cell interior negative relative to the mucosal
bathing medium. Simultaneously, the transmural potential difference (psi m
leads to s) was recorded and its value averaged -0.4 +/- 0.1 mV (serosa
negative). The addition of D-glucose to the mucosal compartment depolarized
psi m to -62.1 +/0 2.5 mV and hyperpolarized psi m leads to s to -1.5 +/-
9.1 mV. Intracellular chloride activity (aCli) was also determined in
Aplysia intestinal cells using single-barreled ion-exchange
microelectrodes. In the absence of D-glucose the mean aCli was 10.1 +/- 0.5
mM, whereas after mucosal glucose addition the paired mean aCli increased
significantly to 14.2 +/- 0.6 mM. Both aCli values were less than those
predicted by the electrochemical equilibrium for chloride across the
mucosal membrane. An active chloride transport mechanism located in the
lateral-serosal membrane of the surface epithelial cells is proposed to
explain these observations.
