T-type voltage gated calcium channels are involved in endothelium-dependent relaxation of mice pulmonary artery.

In pulmonary arterial endothelial cells, Ca channels and intracellular Ca concentration ([Ca]) control the release of vasorelaxant factors such as nitric oxide and are involved in the regulation of pulmonary arterial blood pressure. The present study was undertaken to investigate the implication of T-type voltage-gated Ca channels (T-VGCCs, Ca3.1 channel) in the endothelium-dependent relaxation of intrapulmonary arteries. Relaxation was quantified by means of a myograph in wild type and Ca3.1 mice. Endothelial [Ca] and NO production were measured, on whole vessels, with the fluo-4 and DAF-fm probes. Acetylcholine (ACh) induced a nitric oxide- and endothelium-dependent relaxation that was significantly reduced in pulmonary arteries from Ca3.1 compared to wild type mice as well as in the presence of T-VGCC inhibitors (NNC 55-0396 or mibefradil). ACh also increased endothelial [Ca] and NO production that were both reduced in Ca3.1 compared to wild type mice or in the presence of T-VGCC inhibitors. Immunofluorescence labeling revealed the presence of Ca3.1 channels in endothelial cells that co-localized with endothelial nitric oxide synthase in arteries from wild type mice. TRPV4-, beta2 adrenergic- and nitric oxide donors (SNP)-mediated relaxation were not altered in Ca3.1 compared to wild type mice. Finally, in chronically hypoxic mice, a model of pulmonary hypertension, ACh relaxation was reduced but still depended on Ca3.1 channels activity. The present study thus demonstrates that T-VGCCs, mainly Ca3.1 channel, contribute to intrapulmonary vascular reactivity in mice by controlling endothelial [Ca] and ACh-mediated relaxation.