Calcium signaling in smooth muscle

In this chapter, current topics in the year 1996 about smooth muscle with regards to Ca 2+ storage, Ca 2+ release and reuptake, and Ca 2+ regulation of contraction are discussed. Ca 2+ is mobilized from the endoplasmic reticulum, the physiologically important Ca 2+ reservoir in vascular smooth muscle, through two Ca 2+ -release channels: inositol trisphosphate and the ryanodine receptor. The characteristics, function, and control of these two receptors are summarized. Furthermore, evidence for a role of the nucleus as a potential Ca 2+ storage site is presented and the role of mitochondria and Ca 2+ extrusion systems are discussed. Also, an overview of the current understanding of the mechanism of contraction and relaxation of smooth muscle is given and the modulation of the Ca 2+ sensitivity of the force is discussed.