AJP - Cell Physiology, Vol 260, Issue 5 C934-C948, Copyright © 1991 by American Physiological Society
Whole cell current analyses of pancreatic acinar AR42J cells. I. Voltage- and Ca(2+)-activated currents
K. Kusano and H. Gainer
Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Voltage- and Ca(2+)-activated whole cell currents were studied in AR42J
cells, a clonal cell line derived from rat pancreatic acinar cells, using a
patch electrode voltage-clamp technique. Four kinds of ionic currents were
identified by their ionic dependencies, pharmacological properties, and
kinetic parameters: 1) an outward current flow due mainly to a
voltage-dependent K(+)-conductance increase, 2) an initial transient inward
current due to an Na(+)-conductance increase, 3) transient and
long-duration inward current due to a Ca(2+)-conductance increase, and 4) a
slowly activating inward current that persists over the duration of the
depolarizing pulse and deactivates slowly upon repolarization, producing a
slow inward tail current. The slow inward tail current was particularly
robust and was interpreted as due to a Ca(2+)-activated Cl(-)-conductance
increase, since 1) the generation of this current was blocked by removing
the extracellular Ca2+, applying Ca(2+)-channel blockers (Cd2+,
nifedipine), or by lowering the intracellular Ca2+ concentration [( Ca2+]i)
with EGTA; and 2) the reversal potential (Erev) of the slow inward tail
current was close to 0 mV in the control condition (152 mM [Cl-]o/154 mM
[Cl-]i), and changes of the [Cl-]o/[Cl )i ratio shifted the Erev toward the
predicted Cl- equilibrium potential.
