A whole-cell and single-channel study of the voltage-dependent outward potassium current in avian hepatocytes.


Journal Article

Voltage-dependent membrane currents were studied in dissociated hepatocytes from chick, using the patch-clamp technique. All cells had voltage-dependent outward K+ currents; in 10% of the cells, a fast, transient, tetrodotoxin-sensitive Na+ current was identified. None of the cells had voltage-dependent inward Ca2+ currents. The K+ current activated at a membrane potential of about -10 mV, had a sigmoidal time course, and did not inactivate in 500 ms. The maximum outward conductance was 6.6 +/- 2.4 nS in 18 cells. The reversal potential, estimated from tail current measurements, shifted by 50 mV per 10-fold increase in the external K+ concentration. The current traces were fitted by n2 kinetics with voltage-dependent time constants. Omitting Ca2+ from the external bath or buffering the internal Ca2+ with EGTA did not alter the outward current, which shows that Ca2+-activated K+ currents were not present. 1-5 mM 4-aminopyridine, 0.5-2 mM BaCl2, and 0.1-1 mM CdCl2 reversibly inhibited the current. The block caused by Ba was voltage dependent. Single-channel currents were recorded in cell-attached and outside-out patches. The mean unitary conductance was 7 pS, and the channels displayed bursting kinetics. Thus, avian hepatocytes have a single type of K+ channel belonging to the delayed rectifier class of K+ channels.

Full Text

Cited Authors

  • Marchetti, C; Premont, RT; Brown, AM

Published Date

  • February 1, 1988

Published In

Volume / Issue

  • 91 / 2

Start / End Page

  • 255 - 274

PubMed ID

  • 2453605

Pubmed Central ID

  • 2453605

Electronic International Standard Serial Number (EISSN)

  • 1540-7748

International Standard Serial Number (ISSN)

  • 0022-1295

Digital Object Identifier (DOI)

  • 10.1085/jgp.91.2.255


  • eng