Analysis of the kinetics and voltage-dependency of transient and delayed K+ currents in muscle fibers isolated from the flatworm Schistosoma mansoni.
There are two distinct voltage-dependent K+ currents in muscle fibers freshly isolated from the human flatworm parasite S. mansoni. Present is a delayed rectifier current with a tau act of 17 msec and tau inact > 3 sec. The delayed rectifier is very resistant to steady-state inactivation, with over 40% of the current non-inactivating, and over 15 sec required for the maximum inactivation of the other portion. The current is resistant to block by extracellular tetraethylammonium, is half-blocked by 10 mM 4-aminopyridine, and is insensitive to dendrotoxin. Also present is an "A" current with tau act < 1 msec and tau inact < 15 msec. The "A" current, like the delayed rectifier current, is resistant to block by external tetraethylammonium and is insensitive to dendrotoxin. Three micromoles of 4-aminopyridine produce a half-blockade of the "A" current. These two K+ currents are very similar to a delayed rectifier and "A" currents that have been described in a number of lower and more advanced animals.
Day
T A
TA
Department of Zoology, Michigan State University, East Lansing 48824, USA.
Kim
E
E
Bennett
J L
JL
Pax
R A
RA
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology; D004546:Elapid Venoms / Q000494:pharmacology; D004553:Electric Conductivity; D004594:Electrophysiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D012550:Schistosoma mansoni / Q000033:anatomy & histology* / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D004546:Elapid Venoms; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; C020273:dendrotoxin; D015761:4-Aminopyridine; D002118:Calcium