How selective antagonists and genetic modification have helped characterise the expression and functions of vascular P2Y receptors.

Vascular P2Y receptors mediate many effects, but the role of individual subtypes is often unclear. Here we discuss how subtype-selective antagonists and receptor knockout/knockdown have helped identify these roles in numerous species and vessels. P2Y receptor-mediated vasoconstriction and endothelium-dependent vasodilation have been characterised using the selective antagonists, MRS2179 and MRS2216, whilst AR-C118925XX, a P2Y receptor antagonist, reduced endothelium-dependent relaxation, and signalling evoked by UTP or fluid shear stress.

Characterisation of P2Y receptor subtypes mediating vasodilation and vasoconstriction of rat pulmonary artery using selective antagonists.

Pulmonary vascular tone is modulated by nucleotides, but which P2 receptors mediate these actions is largely unclear. The aim of this study, therefore, was to use subtype-selective antagonists to determine the roles of individual P2Y receptor subtypes in nucleotide-evoked pulmonary vasodilation and vasoconstriction. Isometric tension was recorded from rat intrapulmonary artery rings (i.

Characterisation of P2Y receptors in human vascular endothelial cells using AR-C118925XX, a competitive and selective P2Y antagonist.

Background And Purpose: There is a lack of potent, selective antagonists at most subtypes of P2Y receptor. The aims of this study were to characterise the pharmacological properties of the proposed P2Y receptor antagonist, AR-C118925XX, and then to use it to determine the role of P2Y receptors in the action of the P2Y agonist, UTP, in human vascular endothelial cells.

Experimental Approach: Cell lines expressing native or recombinant P2Y receptors were superfused constantly, and agonist-induced changes in intracellular Ca levels monitored using the Ca -sensitive fluorescent indicator, Cal-520.

Hibiscus acid from Hibiscus sabdariffa (Malvaceae) has a vasorelaxant effect on the rat aorta.

Hibiscus sabdariffa (Malvaceae) is a plant that is widely recognised for its antihypertensive properties; however the constituent(s) responsible for this biological activity are presently unknown. The aim of this study was to identify the potential compounds that are responsible for the vasorelaxant activity of H. sabdariffa.

The Inhibitory Effect of Haloxylon salicornicum on Contraction of the Mouse Uterus.

Haloxylon salicornicum (H. salicornicum) is a plant that is frequently taken as a tea by Bedouin women in Egypt who are experiencing difficulties during pregnancy, as well as to provide relief from dysmenorrhoea. Despite its medical use, there has been no detailed evaluation of the effect of this plant on uterine tissue.

Spontaneous and electrically evoked Ca2+ transients in cardiomyocytes of the rat pulmonary vein.

The pulmonary vein is surrounded by an external sleeve of cardiomyocytes that are widely recognised to play an important role in atrial fibrillation. While intracellular Ca(2+) is thought to influence the electrical activity of cardiomyocytes, there have been relatively few studies examining Ca(2+) signalling in these cells. Therefore, using fluo-4 and fluorescence imaging microscopy, we have investigated Ca(2+) signalling in an intact section of the rat pulmonary vein.

Regulation of store-operated Ca2+ entry in pulmonary artery smooth muscle cells.

Store-operated Ca2+ entry (SOCE) is an important mechanism for Ca2+ influx in smooth muscle cells; however the activation and regulation of this influx pathway are incompletely understood. In the present study we have examined the effect of several protein kinases in regulating SOCE in pulmonary artery smooth muscle cells (PASMCs) of the rat. Inhibition of protein kinase C with chelerythrine (3microM) potentiated SOCE by 47+/-2%, while the tyrosine kinase inhibitors genistein (100microM) and tyrphostin 23 (100microM) caused a significant reduction in SOCE of 55+/-9% and 43+/-7%, respectively.

Pharmacological profile of store-operated Ca(2+) entry in intrapulmonary artery smooth muscle cells.

Store-operated Ca(2+) entry (SOCE) plays an important role in the contraction and proliferation of pulmonary artery smooth muscle cells (PASMCs). The aim of this study was to characterise the pharmacological properties of the SOCE pathway in freshly isolated PASMCs from rat lung and to determine whether this Ca(2+) entry pathway is sensitive to nitric oxide donor drugs. Following depletion of Ca(2+) from the sarcoplasmic reticulum, by treating cells with thapsigargin, re-addition of Ca(2+) produced an increase in cytosolic fluo-4 fluorescence that was sustained for the period that extracellular Ca(2+) was present.

Spontaneous mitochondrial depolarizations are independent of SR Ca2+ release.

The mitochondrial membrane potential (DeltaPsi(m)) underlies many mitochondrial functions, including Ca(2+) influx into the mitochondria, which allows them to serve as buffers of intracellular Ca(2+). Spontaneous depolarizations of DeltaPsi(m), flickers, have been observed in isolated mitochondria and intact cells using the fluorescent cationic lipophile tetramethylrhodamine ethyl ester (TMRE), which distributes across the inner mitochondrial membrane in accordance with the Nernst equation. Flickers in cardiomyocytes have been attributed to uptake of Ca(2+) released from the sarcoplasmic reticulum (SR) via ryanodine receptors in focal transients called Ca(2+) sparks.

The Cl(-) channel blocker niflumic acid releases Ca(2+) from an intracellular store in rat pulmonary artery smooth muscle cells.

The effect of the Cl- channel blockers niflumic acid (NFA), 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), and anthracene-9-carboxylic acid (A-9-C), on Ca2+ signalling in rat pulmonary artery smooth muscle cells was examined. Intracellular Ca2+ concentration ([Ca2+]i) was monitored with either fura-2 or fluo-4, and caffeine was used to activate the ryanodine receptor, thereby releasing Ca2+ from the sarcoplasmic reticulum (SR). NFA and NPPB significantly increased basal [Ca2+]i and attenuated the caffeine-induced increase in [Ca2+]i.

Quantitative analysis of spontaneous mitochondrial depolarizations.

Spontaneous transient depolarizations in mitochondrial membrane potential (DeltaPsi(m)), mitochondrial flickers, have been observed in isolated mitochondria and intact cells using the fluorescent probe, tetramethylrhodamine ethyl ester (TMRE). In theory, the ratio of [TMRE] in cytosol and mitochondrion allows DeltaPsi(m) to be calculated with the Nernst equation, but this has proven difficult in practice due to fluorescence quenching and binding of dye to mitochondrial membranes. We developed a new method to determine the amplitude of flickers in terms of millivolts of depolarization.