Enhancement of K+ currents by stimulation of protein kinase C in the uterine smooth muscle cells of the pregnant rat.
1. Effects of phorbol esters on the K+ currents in isolated rat uterine smooth muscle cells during (18-day) pregnancy were examined using whole-cell voltage-clamp modes. All experiments were performed at room temperature. 2. Test pulses were applied between -20 to + 90 mV from a holding potential of -40 mV. Initially, a transient outward current (ITO) was activated, and outward K+ current (IK) was followed. Threshold potential was - 10 to 0 mV, and the activation was voltage-dependent. At - 80 mV, ITO and IK were 17.8 +/- 3.3 and 13.2 +/- 2.6 pA/pF as a current density. Membrane capacitance was 64.0 +/- 11.5 pF (n = 8). 3. At 0.1 microM, 12-O-tetradecanoylphorbol-13-acetate (TPA) and 4-beta-phorbol-12-13-dibutyrate (PDB) enhanced IK at +80mV by 14.5 +/- 2.0% (n = 8, P < 0.05) and 23.5 +/- 2.2% (n = 7, P < 0.01). Also, ITO at +80mV was increased by 22.1 +/- 2.1% (n = 8, P < 0.01) at 1 microM TPA and by 22.7 +/- 3.0 (n = 7, P < 0.05) at 0.1 microM PDB, significantly. 4. These results indicate that the IK and ITO currents are present in the uterine smooth muscle cells of pregnant rat, and PK-C stimulation modulates the K+ currents, resulting in the regulation of physiological contraction of the uterine muscle during pregnancy.
Satoh
H
H
Department of Pharmacology, Nara Medical University, Japan.
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D018408:Patch-Clamp Techniques; D010703:Phorbol Esters / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D014599:Uterus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*
D004791:Enzyme Inhibitors; D010703:Phorbol Esters; D015221:Potassium Channels; D011493:Protein Kinase C