simultaneous-measurements-intracellular-calcium-membrane-potential

Simultaneous Measurements of Intracellular Calcium and Membrane Potential in Freshly Isolated and Intact Mouse Cerebral Endothelium

Cerebral arteries and their respective microcirculation deliver oxygen and nutrients to the brain via blood flow regulation. Endothelial cells line the ...

isolation-functional-analysis-arteriolar-endothelium-mouse-brain

Isolation and Functional Analysis of Arteriolar Endothelium of Mouse Brain Parenchyma

Cerebral blood flow is conveyed by vascular resistance arteries and downstream parenchymal arterioles. Steady-state vascular resistance to blood flow ...

Loma Linda University

Endothelial cell function in resistance arteries integrates Ca signalling with hyperpolarization to promote relaxation of smooth muscle cells and increase tissue blood flow. Whether complementary signalling occurs in lymphatic endothelium is unknown. Intracellular calcium and membrane potential were evaluated in endothelial cell tubes freshly isolated from mouse collecting lymphatic vessels of the popliteal fossa. Resting membrane potential measured using intracellular microelectrodes averaged ∼-70 mV. Stimulation of lymphatic endothelium by acetylcholine or a TRPV4 channel agonist increased intracellular Ca with robust depolarization. Findings from Trpv4 mice and with computational modelling suggest that the initial mobilization of intracellular Ca leads to influx of Ca and Na through TRPV4 channels to evoke depolarization. Lymphatic endothelial cells lack the Ca -activated K channels present in arterial endothelium to generate endothelium-derived hyperpolarization. Absence of this signalling pathway with effective depolarization may promote rapid conduction of contraction along lymphatic muscle during lymph propulsion.

Calcium and electrical dynamics in lymphatic endothelium.

Electrical signaling along the endothelium underlies spreading vasodilation and blood flow control. We use mathematical modeling to determine the electrical properties of the endothelium and gain insight into the biophysical determinants of electrical conduction.

Biophysical properties of microvascular endothelium: Requirements for initiating and conducting electrical signals.

Electrical dynamics of freshly isolated cerebral endothelium have not been determined independently of perivascular nerves and smooth muscle. We tested the hypothesis that endothelium of cerebral and skeletal muscle arteries differentially utilizes purinergic and muscarinic signaling pathways to activate endothelium-derived hyperpolarization. Changes in membrane potential () were recorded in intact endothelial tubes freshly isolated from posterior cerebral and superior epigastric arteries of male and female C57BL/6 mice (age: 3-8 months).  was measured in response to activation of purinergic (P2Y) and muscarinic (M) receptors in addition to small- and intermediate-conductance Ca-activated K (SK/IK) and inward rectifying K (K) channels using ATP (100 μmol·L), acetylcholine (ACh; 10 μmol·L), NS309 (0.01-10 μmol·L), and 15 mmol·L KCl, respectively. Intercellular coupling was demonstrated via transfer of propidium iodide dye and electrical current (±0.5-3 nA) through gap junctions. With similarities observed across gender, peak hyperpolarization to ATP and ACh in skeletal muscle endothelial tubes was ~twofold and ~sevenfold higher, respectively, vs cerebral endothelial tubes, whereas responses to NS309 were similar (from resting  ~-30 mV to maximum ~-80 mV). Hyperpolarization (~8 mV) occurred during 15 mmol·L KCl treatment in cerebral but not skeletal muscle endothelial tubes. Despite weaker hyperpolarization during endothelial GPCR stimulation in cerebral vs skeletal muscle endothelium, the capability for robust SK/IK activity is preserved across brain and skeletal muscle. As vascular reactivity decreases with aging and cardiovascular disease, endothelial K channel activity may be calibrated to restore blood flow to respective organs regardless of gender.

ArticleTotal : 2	Year
Publication title Cited by 7	2019
Publication title Cited by 2	2022

Article	Year
Calcium and electrical dynamics in lymphatic endothelium. The Journal of physiology\| PubMed ID: 28994159	2017
Biophysical properties of microvascular endothelium: Requirements for initiating and conducting electrical signals. Microcirculation (New York, N.Y. : 1994)\| PubMed ID: 29117630	2018
Electrical dynamics of isolated cerebral and skeletal muscle endothelial tubes: Differential roles of G-protein-coupled receptors and K channels. Pharmacology research & perspectives\| PubMed ID: 29636977	2018

Erik J. Behringer

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