Whole cell current analyses of pancreatic acinar AR42J cells. II. CCK and receptor-activated membrane currents.
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.
Kusano
K
K
Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Gainer
H
H
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002712:Chlorides / Q000494:pharmacology; D002766:Cholecystokinin / Q000378:metabolism / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D010179:Pancreas / Q000166:cytology / Q000502:physiology*; D010190:Pancreatic Neoplasms; D051381:Rats; D011949:Receptors, Cholecystokinin / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology
D015220:Calcium Channels; D002712:Chlorides; D011949:Receptors, Cholecystokinin; D000001:Calcimycin; D004533:Egtazic Acid; D002766:Cholecystokinin; D012964:Sodium