Calcium And Myosin Light Chain Analysis
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Calcium is an important regulator of excitability and contractility in smooth muscle. Intracellular concentrations of Ca2+ are the deciding factor which initiates the muscle contraction process in smooth muscle cells. Incoming Ca2+ via voltage gated channels promotes release of calcium stores from the sarcoplasmic reticulum further increasing cytosolic levels. The Ca2+ induces Ca2+-calmodulin-dependent myosin light chain (MLC) kinase activation. MLC kinase phosphoylates the myosin light chains leading to formation of myosin cross bridges binding to actin, producing a contraction (Sherwood Chp 8)
The majority of Ca2+ required for contraction is derived from the surrounding extra cellular fluid. Smooth muscle cells have a poorly developed sarcoplasmic