Ca2+ Flux Through Voltage-Gated Channels with Flow Cessation in Pulmonary Microvascular Endothelial Cells.

Objective: To investigate the role of voltage-gated Ca²⁺ channels in Ca²⁺ influx with flow cessation in flow-adapted rat pulmonary microvascular endothelial cells. Methods: Cells were evaluated for mRNA and protein levels for major components of the voltage-gated Ca²⁺ channels. Ca²⁺ influx with flow cesastion and cell membrane potential were measured in real time with fluorescent dyes. Mibefradil and nifedipine were used as inhibitors of Ca²⁺ channel activity. Results: Voltage-gated Ca²⁺ channel protein and mRNA for the T-type channel were expressed at a relatively low level in endothelial cells cultured under static conditions and expression was induced significantly during flow adaptation. Flow-adapted but not control cells showed Ca²⁺ influx during flow cessation that was blocked by mibefradil but not by nifedipine. Ca²⁺ influx also was blocked by cromakalim, a K_ATP channel agonist. Cell membrane depolarization with flow cesastion was unaffected by mibefradil. Conclusions: Rat pulmonary microvascular endothelial cells express T-type voltage-gated Ca²⁺ channels that are induced during adaptation to flow and are responsible for Ca²⁺ influx that occurs as a result of flow cessation-mediated membrane depolarization. [ABSTRACT FROM AUTHOR]