Elementary calcium signaling in arterial smooth muscle

Vascular smooth muscle cells (VSMCs) of small peripheral arteries contribute to blood pressure control by adapting their contractile state. These adaptations depend on the VSMC cytosolic Ca(2+) concentration, regulated by complex local elementary Ca(2+) signaling pathways. Ca(2+) sparks represent local, transient, rapid calcium release events from a cluster of ryanodine receptors (RyRs) in the sarcoplasmic reticulum. In arterial SMCs, Ca(2+) sparks activate nearby calcium-dependent potassium channels, cause membrane hyperpolarization and thus decrease the global intracellular [Ca(2+)] to oppose vasoconstriction. Arterial SMC Ca(v)1.2 L-type channels regulate intracellular calcium stores content, which in turn modulates calcium efflux through RyRs. Ca(v)3.2 T-type channels contribute to a minor extend to Ca(2+) spark generation in certain types of arteries. Their localization within cell membrane caveolae is essential. We summarize present data on local elementary calcium signaling (Ca(2+) sparks) in arterial SMCs with focus on RyR isoforms, large-conductance calcium-dependent potassium (BK(Ca)) channels, and cell membrane-bound calcium channels (Ca(v)1.2 and Ca(v)3.2), particularly in caveolar microdomains.