Voltage-gated currents in muscle cells of Schistosoma mansoni.
Three morphologically distinct types of muscle fibres isolated from the platyhelminth Schistosoma mansoni have been studied with whole cell current- and voltage-clamp techniques. Fibres showed a marked time-dependent decrease in membrane resistance in response to depolarizing current injections. Voltage-clamp experiments revealed the presence of two distinct voltage-gated outward currents. The most prominent current is a slowly activating, slowly and incompletely inactivating potassium current similar to delayed rectifier currents which have been described in a variety of cell types from a variety of organisms. Also present is a faster activating, quickly and completely inactivating potassium current that shares functional characteristics with 'A'-currents. All three of the cell types studied possess a delayed rectifier current, but only two of the three types have 'A'-currents. Though depolarization with high K+ leads to contraction of the dispersed fibres, no voltage-gated inward currents could be detected by whole cell voltage-clamp under any of our conditions.
Day
T A
TA
Department of Zoology, Michigan State University, East Lansing 48824.
Orr
N
N
Bennett
J L
JL
Pax
R A
RA
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015640:Ion Channel Gating; D008564:Membrane Potentials; D009119:Muscle Contraction / Q000502:physiology; D009132:Muscles / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D012550:Schistosoma mansoni / Q000502:physiology*
D011188:Potassium; D002118:Calcium