Increase in cytosolic calcium from intracellular storage, during smooth muscle contraction, is/are due to -
The release of Ca++ from intracellular source, that is sarcoplasmic reticulum, is by IP3-DAG second messenger system, whereas the pumping of Ca++ from extracellular space to cytosol is by Ca++ channels. 
IP3 when bound to its receptors on sarcoplasmic reticulum, causes the release of calcium into sarcoplasm.
cAMP
cGMP
cCMP
IP3-DAG