New Findings What is the central question of this study?The aim was to examine and compare the contributions of caveolin‐1 to the contractile responses mediated by L‐type voltage‐dependent calcium channels, store‐operated Ca2+ channels and receptor‐operated Ca2+ channels in two different types of arteries from two‐kidney, one‐clip hypertensive rats. What is the main finding and its importance?We demonstrated that the density of caveolae and caveolin‐1 expression were significantly upregulated in the aorta of two‐kidney, one‐clip hypertensive rats, but not in the third‐order branches of mesenteric arteries. We highlight that caveolin‐1 plays an important role in aortic constriction by enhancing receptor‐operated Ca2+ entry in the hypertensive rat model. Abstract Calcium and its multiple regulatory mechanisms are crucial for the development of hypertension. Among these regulatory mechanisms, store‐operated Ca2+ entry (SOCE) and receptor‐operated Ca2+ entry (ROCE) mediate agonist‐induced calcium influx, contributing to vascular contraction. The SOCE and ROCE are regulated by a variety of mechanisms involving caveolin‐1 (Cav1), which has been found to be strongly associated with hypertension in gene polymorphism. In the present study, we investigated the role of Cav1 during the enhanced activity of calcium channels in hypertensive arteries. We demonstrated that the expression level of Cav1 was significantly increased in the aorta of two‐kidney, one‐clip (2K1C) hypertensive rats. The disruption of caveolae by methyl‐β‐cyclodextrin did not cause a marked difference in agonist‐induced vasoconstriction in the third‐order branches of the mesenteric arteries but strongly suppressed the aortic contractile response to endothelin‐1 in the 2K1C group, which was not found in the control group. The increase in Cav1 by introduction of Cav1 scaffolding domain enhancing peptide promoted the 1‐oleoyl‐2‐acetyl‐glycerol‐induced ROCE in hypertensive aortic smooth muscle cells but did not enhance the cyclopiazonic acid‐induced SOCE. In the resistance arteries, similar changes were not observed, and no statistical changes of Cav1 expression were evident in the third‐order branches of the mesenteric arteries. Our results indicate that increased Cav1 expression might promote the altered [Ca2+]i‐induced aortic vasoreactivity by enhancing ROCE and be involved in the pathogenesis of hypertension.

Increased extracellular magnesium concentration has been shown to attenuate the endothelin-1-induced contractile response via the release of nitric oxide (NO) from the endothelium in proximal pulmonary arteries (PAs) of chronic hypoxic mice. Here, we further examined the involvement of Mg 2+ in the inhibition of vasoconstriction in PAs and distal smaller pulmonary arteries (sPAs) in a monocrotaline-induced pulmonary arterial hypertension (MCT-PAH) rat model. The data showed that in control rats vasoconstriction in sPAs is more intense than that in PAs. In MCT-PAH rats, store-operated Ca 2+ entry (SOCE)-and receptor-operated Ca 2+ entry (ROCE)-mediated contraction were significantly strengthened. However, there was no upregulation of the vasoconstriction mediated by voltage-dependent calcium entry (VDCE). Furthermore, high magnesium greatly inhibited VDCE-mediated contraction in PAs rather than sPAs, which was the opposite of the ROCE-mediated contraction. Moreover, monocrotaline pretreatment partly eliminated the endothelium-dependent vasodilatation in PAs, which in sPAs, however, was still promoted by magnesium due to the increased NO release in pulmonary microvascular endothelial cells (PMVECs). In conclusion, the findings suggest that both SOCE-and ROCE-mediated vasoconstriction in the MCT-PAH model are enhanced, especially in sPAs. The inhibitory effect of high magnesium on vasoconstriction can be achieved partly by its direct role as a Ca 2+ antagonist and partly by increasing NO release in PMVECs.

Objectives To detect the vascular tension and nitric oxide (NO) release synchronously in mice pulmonary artery, we perform two experiments and present a novel application of confocal wire myograph coupled with the confocal laser scanning microscopy. Methods In the first experiment, viable endothelium-intact mouse pulmonary artery (outer diameter 100–300 μM) rings underwent a one-hour preincubation with a NO-specific fluorescent dye, 4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate Calbiochem (2.5 μM), and then precontracted with phenylephrine (Phen, 10−6 M), and subsequently dilated in acetylcholine (ACh, 10−6 M – 10−4 M). The endothelium-dependent vasorelaxation and NO generation in pulmonary artery rings were simultaneously recorded. In the second experiment, after 30-min incubation with the former NO fluorescent dye, the qualified pulmonary artery rings were co-incubated for another 30 min with a nitric oxide synthase inhibitor, 10−4 M Nω-nitro-L-arginine-methyl-ester (L-NAME), and then pretreated with Phen (10−6 M) followed by ACh (10−5 M). The Ach-induced vasodilation and NO release were recorded simultaneously. Results ACh (10−6 M – 10−4 M) promoted pulmonary artery relaxation and intracellular NO release in a dose-dependent manner. Additionally, L-NAME (10−4 M) significantly attenuated the vasodilatation and the intracellular NO release. Conclusions This combined application visually confirms that the synchronous changes in Ach induced vasodilation and NO release, which provides a new method for cardiovascular research.