Insulin Depolarization of Rat Hepatocytes in Primary Monolayer Culture

Document Type

Article

Publication Date

1-1-1983

Description

Rat hepatocytes in primary monolayer culture demonstrated two stable states of transmembrane potential (E(m)). Low potentials ranging from -10 to -15 mV followed impalements with glass microelectrodes, and in some cells low potentials increased spontaneously or in response to a train of intermittent current (5 nA) to stable potentials of -50 mV, which were comparable to hepatocyte E(m) in vivo. Adding insulin at 20 mU/ml depolarized the stable higher E(m) 22.4 ± 2.6 mV (n = 6) over an 11-min interval, and input resistance increased 21.4 ± 4.7 MΩ (n = 6) during the depolarization. The insulin effect was dose dependent, because adding insulin at 0.2 mU/ml depolarized the stable high E(m) 5.0 ± 1.5 mV (n = 3) and increased input resistance 6.3 ± 1.8 MΩ (n = 3). In one experiment the E(m) repolarized 32 min after insulin was washed out. Adding metabolic inhibitors KCN (1 mM) and 2,4-dinitrophenol (10 and 1 mM) and increasing external potassium (60 mM, with external sodium reduced equivalently) also depolarized E(m), but they did not increase input resistance. Thus insulin depolarized hepatocytes from a stable high E(m), which is equivalent to the E(m) of liver in vivo, to a stable low E(m), which occurs in hepatocytes in primary monolayer culture. This hormone action is consistent with changes in membrane ion conductance, and it further demonstrates that these cells can sustain two stable states of E(m).

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