AJP - Cell Physiology, Vol 260, Issue 5 C949-C957, Copyright © 1991 by American Physiological Society
Whole cell current analyses of pancreatic acinar AR42J cells. II. CCK and receptor-activated membrane currents
K. Kusano and H. Gainer
Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Receptor currents generated in response to the application of sulfated
octa-cholecystokinin (CCK) and various pancreatic secretagogues were
studied in AR42J cells, a rat pancreatic acinar cell line. A whole cell
configuration of the patch electrode voltage-clamp technique was utilized
in these studies. Over 60% of the cells examined responded to 10(-6) M CCK
by generating inward current at a membrane holding potential of -70 mV,
accompanied by an increased membrane conductance. The CCK-induced receptor
current (ICCK) was typically inactivated within 30 s in the presence of the
ligand. The reversal potential (Erev) of the ICCK was approximately 0 mV
when recorded in control bathing solution with a pipette containing 154 mM
Cl-. When Cl- concentration in the bathing solution or in the recording
pipette was modified, the Erev of the ICCK shifted toward the predicted Cl-
potential. Na+ and K+ did not show significant contributions to the Erev of
ICCK. Hence, the ICCK involves an increased Cl- conductance. This increased
Cl- conductance appears to be due to an increase in intracellular Ca2+,
since the ICCK could not be recorded from cells using pipettes containing 5
mM EGTA. Application of a Ca2+ ionophore A23187 (5 microM) to cells in
control saline induced a similar inward current flow. The source of the
Ca2+ involved in the ICCK appears to be mainly intracellular, since the
ICCK could be recorded under conditions designed to completely block the
voltage-dependent Ca2+ entry. These included exposure of the cells to a
Ca2(+)-free saline for a brief period or the presence of 500 microM Cd2+ in
the control bathing solution.
