Slow-delayed rectifier channels

Zhou, Y. Y., Yao, J. A., and Tsen, G. N. 1997. Role of tyrosine kinase activity in cardiac slow delayed rectifier channel modulation by cell swelling. Pfliigers Arch. 433 750-757. 

Voltage-gated channels Kyi to Ky9, which a- subunit contains 6 transmembrane helices with a single pore, including also the slow delayed rectifiers Ky(g) (or Ky LTQ), and the rapid delayed rectifiers Ky( ) (or KyEAG-like). The old experimental blocker of Ky channels, 4-aminopyridine, is in phase 3 in the treament of multiple sclerosis. ... 

For the most part the selective Class III agents appear to act by inhibition of one or more repolarizing potassiuim currents, especially the delayed rectifier (/k) and/or the inward rectifier (/ki). Less selective agents generally affect sodium currents, as well as potassium currents, which translates to Class I (conduction-slowing) activity. Additional work still needs to be done to increase our understanding of the currents and channels involved in regulation of APD. Care must be taken to evaluate species differences, tissue dif-... 

Outward repolarizing currents oppose the effect of the inward Ica on the plateau phase. This current is carried predominantly through delayed rectifier potassium channels (Ik).These channels are voltage sensitive, with slow inactivation kinetics. Three distinct subpopulations of Ik with differing activation and inactivation kinetics have been described. A rapidly activating subset (Ikf), a slowly inactivating subset (Iks), and an ul-tra-rapidly activating subset to date are identified only in atrial tissue (Ikui)-... 

Dofetilide has class 3 action potential prolonging action. This action is effected by a dose-dependent blockade of the rapid component of the delayed rectifier potassium current, IKr, and the blockade of IKr increases in hypokalemia. Dofetilide produces no relevant blockade of the other potassium channels or the sodium channel. Because of the slow rate of recovery from blockade, the extent of blockade shows little dependence on stimulation frequency. However, dofetilide does show less action potential prolongation at rapid rates because of the increased importance of other potassium channels such as IKs at higher frequencies. 

Fast sodium current (/Na) slow calcium current (L-type channels /ca) sodium/calcium exchange current (/Na/Ca) inward potassium rectifier current (/ki) transient currents (7,o) rapid delayed potassium rectifier current (/ks) slow potassium delayed rectifier current (/kt)... 

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