Protein kinase C inhibits delayed rectifier potassium current in rabbit vascular smooth muscle cells.

AIELLO EA; CLEMENT-CHOMMIENE O; SONTAG DP; WALSH MP; COLE WC

AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY

AMER PHYSIOLOGICAL SOC

Lugar: Bethesda; Año: 1996 vol. 271 p. 109 - 119

0363-6135

The effect of protein kinase C (PKC) activation on 4-aminopyridine (4- AP)-sensitive delayed rectifier current (I(dK)) was studied in isolated rabbit portal vein smooth muscle cells by use of standard whole cell voltage clamp. The effects of the phorbol ester, 4?-phorbol 12,13-dibutyrate (PdBu, 100 nM) and diacylglycerol analogues, 1,2-dioctanoyl-sn-glycerol (1,2-diC8, 10 ?M) and 1,3-dioctanoyl-sn-glycerol (1,3-diC8, 10 ?M), on macroscopic whole cell l(dK) were assessed in myocytes dialyzed with 10 mM 1,2-bis(2- aminophenoxy)ethane-N,N,N´,N´-tetraacetic acid (BAPTA) and 5 mM ATP (20- 22°C). Activation of PKC by 1,2-diC8 or PdBu caused a decline in l(dK) that was reversed with washout of drug. 1,2-diC8 had no effect on outward current present after exposure to 4-AP (20 mM). The inactive analogue, 1,3-diC8, did not affect I(dK), but subsequent exposure to the active analogue, 1,2-diC8, caused a marked depression of the current. The inhibition of I(dK) by 1,2- diC8 was significantly reduced by intracellular dialysis with the inhibitors of PKC, chelerythrine (50 ?M) and calphostin C (1 ?M). Substitution of extracellular Ca2+ with Mg2+ in the presence of 10 mM intracellular BAPTA did not affect the suppression of I(dK) by 1,2-diC8, indicating the involvement of a Ca2+-independent isoform of PKC. This study suggests a novel signal transduction mechanism for inhibition of 4-AP-sensitive I(dK) involving a phosphotransferase reaction catalyzed by PKC in vascular smooth muscle myocytes.