Linoleic acid both enhances activation and blocks Kv1.5 and Kv2.1 channels by two separate mechanisms.
Linoleic acid (LA) had two effects on human Kv1.5 and Kv2.1 channels expressed in Chinese hamster ovary cells: an increase in the speed of current activation process (EC(50) = 2.4 and 2.7 microM for Kv1.5 and Kv2.1, respectively) and current inhibition (IC(50) = 6.6 and 7.4 for Kv1.5 and Kv2.1, respectively). LA affected the activation kinetics via two processes: a leftward shift in the instantaneous activation curves and an increase in the rate of current rise. Current inhibition by LA was time dependent but voltage independent. Hill slopes for plots of current inhibition (3.5 and 3.9 for Kv1.5 and Kv2.1, respectively) vs. dose of LA suggested that cooperativity was involved in the mechanism of current inhibition. A similar analysis of the effects of LA on current activation did not reveal cooperative interactions. The effects of LA were mediated from the external side of the channels, since addition of 10 microM LA to the patch pipette solution was without effect. Additionally, the methyl ester of LA was effective at enhancing peak current and promoting channel activation for Kv1.5 and Kv2.1 without inducing significant current inhibition.
McKay
M C
MC
Department of Molecular Endocrinology, GlaxoSmithKline, Inc., Research Triangle Park, North Carolina 27709, USA. cym9845@gsk.com
Worley
J F
JF
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D051668:Delayed Rectifier Potassium Channels; D004594:Electrophysiology; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D051666:Kv1.5 Potassium Channel; D019787:Linoleic Acid / Q000494:pharmacology*; D008041:Linoleic Acids / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D051669:Shab Potassium Channels
D051668:Delayed Rectifier Potassium Channels; D051666:Kv1.5 Potassium Channel; D008041:Linoleic Acids; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051669:Shab Potassium Channels; C005575:methyl linoleate; D019787:Linoleic Acid