Calcium-induced calcium release mechanism in vascular smooth muscles--assessments based on contractions evoked in intact and saponin-treated skinned muscles.

This article was concerned with the role of Ca in triggering the contraction in vascular smooth muscles. Whenever Ca influx is activated, this Ca does not directly activate the contractile proteins, but rather triggers the release of Ca from the SR to activate calmodulin. This release of Ca by Ca is dependent on the amount of Ca stored within the cells. Voltage dependent Ca influx activated by excess concentrations of K, electrical depolarization and Ca spikes is required to produce the contraction through activation of the Ca-induced Ca release mechanism. The elucidation of the contribution of the P-I response for Ca mobilization through activation of receptors under physiological conditions hopefully will lend support to our hypothesis.