Enhancement of K + currents by stimulation of protein kinase C in the uterine smooth muscle cells of the pregnant rat

Abstract

1. 1. Effects of phorbolesters 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. 2. Test pulses were applied between − 20 to + 90 mV from a holding potential of − 40 mV. Initially, a transient outward current (I TO) was activated, and an outward K + current (I K) was followed. Threshold potential was − 10 to 0 mV, and the activation was voltage-dependent. At - 80 mV, I TO 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. 3. At 0.1 μM, 12-O-tetradecanoylphorbol-13-acetate (TPA) and 4-β-phorbol-12-13-dibutyrate (PDB) enhanced I K at +80mV by 14.5±2.0% ( n=8, P<0.05) and 23.5±2.2% ( n=7, P<0.01). Also, I TO at +80mV was increased by 22.1±2.1% ( n=8, P<0.01) at 1 μM TPA and by 22.7±3.0 ( n=7, P<0.05) at 0.1 μM PDB, significantly. 4. 4. These results indicate that the I K and I TO 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.