CYCLOPIAZONIC ACID STIMULATES CA2-CELLS( INFLUX THROUGH NONSPECIFIC CATION CHANNELS IN ENDOTHELIAL)

A non-specific cation channel in cultured human umbilical vein endothe lial cells was obtained by cell-attached patch-clamp study. This chann el showed a conductance of 28 pS when both pipette and bath contained 140 mM potassium chloride. when pipette solution was changed into 140 sodium chloride with 5 mM calcium chloride, the conductance was 26 pS. when 120 mM calcium chloride was used as the only cation in the pipet te, a conductance of 6 pS was obtained. Bath application of cyclopiazo nic acid, an inhibitor of the sarcoplasmic reticulum Ca2+ pump in smoo th muscle and other tissues, dose dependently activates this non-speci fic cation channel. It is assumed that cyclopiazonic acid by blockade of the refilling of Ca2+ stores depletes the rapidly exchanging intrac ellular Ca2+ stores and this action stimulates Ca2+ influx through the non-specific cation channels in human umbilical vein endothelial cell s.A non-specific cation channel in cultured human umbilical vein endot helial cells was obtained by cell-attached patch-clamp study. This cha nnel showed a conductance of 28 pS when both pipette and bath containe d 140 mM potassium chloride. when pipette solution was changed into 14 0 sodium chloride with 5 mM calcium chloride, the conductance was 26 p S. when 120 mM calcium chloride was used as the only cation in the pip ette, a conductance of 6 pS was obtained. Bath application of cyclopia zonic acid, an inhibitor of the sarcoplasmic reticulum Ca2+ pump in sm ooth muscle and other tissues, dose dependently activates this non-spe cific cation channel. It is assumed that cyclopiazonic acid by blockad e of the refilling of Ca2+ stores depletes the rapidly exchanging intr acellular Ca2+ stores and this action stimulates Ca2+ influx through t he non-specific cation channels in human umbilical vein endothelial ce lls.