Smooth Muscle Contraction

Relaxation of the smooth muscle takes place due to the absence of the contractile stimulus or through the presence of a substance, which induces the inhibition of the mechanism that initiates contraction. For this process to take place, low levels of intracellular Ca2+concentration are required along with high MLC phosphatase activity. Reduction in calcium release from the SR or reduction of calcium entry into the cell can cause this reduction in the phosphorylation of MLC. There are several mechanisms involved in the removal of cytosolic calcium. ATP hydrolysis determines the level of Ca2+ uptake in which the phosphorylation of CaMg-ATPase (also found in the plasma membrane) leads to two Ca2+ ions to bind and is transferred to the luminal