Regulation of ion channels in rat hepatocytes.
Patch-clamp studies have been performed to elucidate single ion channels in rat hepatocytes. In rat hepatocytes two types of ion channel have been identified: an inwardly rectifying K+ channel with a mean inward conductance of 55 +/- 6.5 pS (n = 20) and a mean outward conductance of 25 +/- 3.2 pS (n = 20) in the inside-out configuration with 145 mmol/l KCl on either side of the patch as well as an outwardly rectifying Cl- channel with a mean outward conductance of 30 +/- 4.5 pS (n = 8) and a mean inward conductance of 10 +/- 2.3 pS (n = 6) in the inside-out configuration with symmetrical 145 mmol/l KCl. The open probability of these channels is virtually insensitive to Ca2+ activity on the intracellular side. Accordingly, the Ca2+ ionophore ionomycin had no effect on cell membrane potential. Dibutyryl-cAMP (db-cAMP) hyperpolarizes the cell membrane and increases the activity of the 55-pS inwardly rectifying K+ channel by reducing the duration of closure between bursts. Forskolin similarly hyperpolarizes the cell membrane. The inwardly rectifying K+ channel is inhibited by progesterone, while the outwardly rectifying Cl- channel is insensitive to progesterone.
Breit
S
S
Physiologisches Institut, Universität Tübingen, Gmelinstrasse 5, D-72076 Tübingen, Germany.
Kolb
H
H
Apfel
H
H
Haberland
C
C
Schmitt
M
M
Häussinger
D
D
Graf
J
J
Lang
F
F
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D004553:Electric Conductivity; D006801:Humans; D015640:Ion Channel Gating; D007473:Ion Channels / Q000502:physiology*; D015759:Ionomycin / Q000494:pharmacology; D008099:Liver / Q000502:physiology*; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats
D018118:Chloride Channels; D007473:Ion Channels; D015221:Potassium Channels; D005576:Colforsin; D015759:Ionomycin; D003994:Bucladesine; D011189:Potassium Chloride; D002118:Calcium