title: Modulation of the delayed rectifier, IK, by cadmium in cat ventricular myocytes.
abstract: The effects of cadmium on the delayed outward potassium current (IK) were investigated in isolated cat ventricular myocytes using the single suction pipette voltage-clamp technique. IK activation was examined using peak tail currents elicited after 750-ms voltage-clamp steps to selected membrane potentials from a holding potential of -40 mV. In the presence of Cd2+ (0.2 mM), peak tail currents increased from a control value of 85 +/- 12 to 125 +/- 18 pA (n = 4). Activation curves constructed from the average peak tail-current measurements in all experiments showed that Cd2+ shifted the voltage dependence of activation to more positive potentials by 16.4 +/- 2.0 mV and increased the slope factor of the activation curve from 6.1 +/- 0.2 to 6.9 +/- 0.2 mV. In the absence of Cd2+, increases in holding potential from -30 to -70 mV had no effect on the magnitude of the peak tail currents, suggesting that the Cd(2+)-induced increase was not the result of a voltage-dependent increase in the number of available K+ channels at the holding potential. Slow voltage ramps from -70 to +70 mV revealed that Cd2+ increased the outward current at membrane potentials positive to +20 mV and shifted the voltage range in which IK inwardly rectified to more positive potentials. The fully activated current-voltage relationship was also shifted to more positive potentials by Cd2+. Cd2+ did not alter channel selectivity for K+.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Cardiovascular Pharmacology, Wyeth-Ayerst Research, Princeton, New Jersey 08543-8000.
authors.forename: C H
authors.initials: CH
authors.lastname: Follmer
authors.forename: N J
authors.initials: NJ
authors.lastname: Lodge
authors.forename: C A
authors.initials: CA
authors.lastname: Cullinan
authors.forename: T J
authors.initials: TJ
authors.lastname: Colatsky
mesh_terms: D000818:Animals; D002104:Cadmium / Q000494:pharmacology*; D002415:Cats; D004594:Electrophysiology; D006352:Heart Ventricles; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology
chemical_list: D015221:Potassium Channels; D002104:Cadmium