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Updated: Aug 2, 2026

Focal Ca2+ Transient Detection in Smooth Muscle
Published on: June 29, 2009
Smooth muscle sarcolemma-associated phospholipase C-beta 2; agonist-evoked translocation
R F Coburn1, E F Labelle, T Griffiths
1Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, USA.
Abstract:
About 25% of the total cellular PLC beta 2 content was found to be associated with a sarcolemmal fraction (SARC) isolated from unstimulated porcine trachealis smooth muscle. SARC-associated PLC beta 2 was located within two compartments, a detergent-extractable compartment and a nondetergent extractable compartment. SARC PLC beta 2 was measured after extraction with 0.6 M KCI; therefore, PLC beta 2 was not bound solely by electrostatic forces within either of these compartments. PLC beta 2 was shown to translocate from cytosol to SARC during a 20-sec activation of intact muscle with a muscarinic agonist, carbachol (CARB); i.e., cytosolic total PLC beta 2 content decreased significantly to 73 +/- 7% of control and SARC total PLC beta 2 content increased to 180 +/- 15% of control value. This translocation was maintained at 5 min of CARB. CARB-evoked translocation occurred into the detergent-extractable SARC fraction, and PLC beta 2 content in this fraction increased 300% compared with that in unstimulated muscle. After CARB, SARC PLC beta 2 content accounted for > 50% of total cellular PLC beta 2 content. CARB-evoked increase in PLC activity in SARC paralleled the increase in PLC beta 2 content. CARB-induced translocations of PLC beta 2 from the cytosol to SARC were of a similar magnitude as occurred with phorbol ester-induced translocations of PKC alpha.
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