ISSN:
1432-1424
Keywords:
calcium current
;
skeletal muscle
;
sulfhydryl
;
invertebrate muscle
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Voltage-clamp experiments using the three-microelectrode voltage clamp technique were performed on ventroabdominal flexor muscles of the crustacean Atya lanipes. Potassium and chloride currents were found to underlie the normal, passive response of the muscle. Blocking potassium currents with tetraethylammonium and replacing chloride ions with methanesulfonate did not unmask an inward current. By treating the muscle with the sulfhydryl-alkylating agent 4-cyclopentene-1,3-dione an inward current was detected. The current induced by the agent is carried by Ca2+, since it is abolished in Ca2+-free solutions. The induced Ca+current is detected at about -40 mV and reaches a mean maximum value of -78 μA/cm2 at ca. -10 mV. At this potential the time to peak is close to 15 msec.The induced Ca2+ current inactivated with 1-sec prepulses which did not elicit detectable Ca2+ current; the fitted h xcurve had a midpoint of-38 mV and a steepness of 5.0 mV. Measurements of isometric tension were performed in small bundles of fibers, and the effects of the sulfhydryl-alkylating agents 4-cyclopentene-1,3-dione andN-ethylmaleimide were investigated. Tetanic tension was enhanced in a strictly Ca2+-dependent manner by 4-cyclopentene1,3-dione. The amplitude of K+ contractures increased after treatment with N-ethylmaleimide. It is concluded that Ca2+ channels are made functional by the sulfhydryl-specific reagents and that the increase in tension is probably mediated by an increase in Ca2+ influxthrough the chemically induced Ca2+ channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00219512
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