Hyperactivation is initiated by extracellular calcium; however, the factors that regulate calcium level is unknown.

Ultimately, these two messengers result in a release of calcium from intracellular stores and a subsequent flux of extracellular calcium into the cytoplasmic space.

Influx of extracellular calcium and agonist-coupling appear essential for the activation of thromboxane A2-dependent phospholipase A2 in human platelets.

Phospholipase A2 activation in human neutrophils requires influx of extracellular calcium and leukotriene B4.

'There is a precedent for that', he claims, noting that extracellular calcium is sensed by a GPCR.

Experiments have shown that in reduced extracellular calcium, the myosin motor tightens, resulting in more open channels.

Further different smooth muscle tissues display extremes of abundant to little sarcoplasmic reticulum so excitation-contraction coupling varies with its dependence on intracellular or extracellular calcium.

In comparison, signalling of the homologous D-D receptor heteromer involves the influx of extracellular calcium.

"To everyone's surprise, he showed that the contractions could be controlled by changes in the extracellular calcium," Dr. Andersen said.

In some experiments extracellular calcium was chelated by pre-treating the cells with 3 mM EGTA for 15-min.