Sarcoplasmic reticulum and endothelium independently regulate venous smooth muscle [Ca]i and contraction
نویسندگان
چکیده
Laporte, Régent, and Ismail Laher. Sarcoplasmic reticulum and endothelium independently regulate venous smooth muscle [Ca]i and contraction. Am. J. Physiol. 277 (Heart Circ. Physiol. 46): H749–H755, 1999.—In rings of rabbit facial vein (RFV), depletion of sarcoplasmic reticulum (SR) Ca21 by caffeine abolished the subsequent isometric contraction to 25 mM K1 physiological salt solution (25K-PSS). However, the associated steady-state increase of smooth muscle intracellular free Ca21 concentration ([Ca]i), measured using fura PE3 and cuvette photometry, was not altered. Treatment with the specific SR Ca21 pump inhibitor cyclopiazonic acid (30 μM) after caffeine-induced SR Ca21 depletion restored and greatly augmented the 25K-PSSinduced contraction. This suggests that SR Ca21 depletion leads to a dissociation of K1-induced [Ca]i increase from contraction that was dependent on Ca21 pump-mediated SR Ca21 uptake. Endothelium removal augmented the 25K-PSSinduced [Ca]i increase after caffeine-induced SR Ca21 depletion. However, this was associated with only a small and transient contraction. Exposure of endothelium-denuded RFV to cyclopiazonic acid after caffeine-induced SR Ca21 depletion further amplified the 25K-PSS-induced [Ca]i increase, which was associated with a large and sustained contraction. However, the latter [Ca]i increase was still higher than in endothelium-intact RFV. This suggests that the endothelium dampens the [Ca]i rise associated with K1-induced Ca21 influx, but independently of Ca21 pump-mediated SR Ca21 uptake.
منابع مشابه
Sarcoplasmic reticulum and endothelium independently regulate venous smooth muscle [Ca2+]iand contraction.
In rings of rabbit facial vein (RFV), depletion of sarcoplasmic reticulum (SR) Ca2+ by caffeine abolished the subsequent isometric contraction to 25 mM K+ physiological salt solution (25K-PSS). However, the associated steady-state increase of smooth muscle intracellular free Ca2+concentration ([Ca2+]i), measured using fura PE3 and cuvette photometry, was not altered. Treatment with the specific...
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