Bromo-eudistomin D induced a contraction of the chemically skinned fibers from skeletal muscle at concentrations of 10 μM or more. This contractile response to bromo-eudistomin D was completely blocked by 10 mM procaine. The extravascular Ca2+ concentrations of the heavy fractions of the fragmented sarcoplasmic reticulum (HSR) were measured directly by a Ca2+ electrode to examine the effect of bromo-eudistomin D on the sarcoplasmic reticulum. After the HSR was loaded with Ca2+ by the ATP-dependent Ca2+ pump, the addition of 10 μM bromo-eudistomin D caused Ca2+ release that was followed by spontaneous Ca2+ reuptake. In the presence of 2 μM ruthenium red or 4 mM MgCl2, no Ca2+ release was induced by 20 μM bromo-eudistomin D. The rate of 45Ca2+ efflux from HSR, which had been passively preloaded with 45Ca2+, was accelerated 7 times by 10 μM bromo-eudistomin D. The concentration of bromo-eudistomin D for half-maximum effect on the apparent efflux rate was 1.5 μM, while that of caffeine was 0.6 mM. The bromo-eudistomin D-evoked efflux of 45Ca2+ was abolished by 2 μM ruthenium red or 0.5 mM MgCl2. Bromo-eudistomin D was found to be 400 times more potent than caffeine in its Ca2+-releasing action but was similar in its action in other respects. These results indicate that bromo-eudistomin D may induce Ca2+ release from the sarcoplasmic reticulum through physiologically relevant Ca2+ channels.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of Biological Chemistry|
|State||Published - 1986|
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