Postischemic reperfusion causes smooth muscle calcium sensitization and vasoconstriction of parenchymal arterioles. 2014

Marilyn J Cipolla, and Siu-Lung Chan, and Julie Sweet, and Matthew J Tavares, and Natalia Gokina, and Joseph E Brayden
From the Department of Neurological Sciences (M.J.C., S.-L.C., J.S.), Department of Pharmacology (M.J.C., M.J.T., J.E.B.), and Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Vermont, Burlington (M.J.C., N.G.). Marilyn.Cipolla@uvm.edu.

OBJECTIVE Parenchymal arterioles (PAs) are high-resistance vessels in the brain that connect pial vessels to the microcirculation. We previously showed that PAs have increased vasoconstriction after ischemia and reperfusion that could increase perfusion deficit. Here, we investigated underlying mechanisms by which early postischemic reperfusion causes increased vasoconstriction of PAs. METHODS Isolated and pressurized PAs from within the middle cerebral artery territory were studied in male Wistar rats that were either nonischemic control (n=34) or after exposure to transient middle cerebral artery occlusion (MCAO) by filament occlusion for 2 hours with 30 minutes of reperfusion (MCAO; n=38). The relationships among pressure-induced tone, smooth muscle calcium (using Fura 2), and membrane potential were determined. Sensitivity of the contractile apparatus to calcium was measured in permeabilized arterioles using Staphylococcus aureus α-toxin. Reactivity to inhibition of transient receptor potential melastanin receptor type 4 (9-phenanthrol), Rho kinase (Y27632), and protein kinase C (Gö6976) was also measured. RESULTS After MCAO, PAs had increased myogenic tone compared with controls (47±2% versus 35±2% at 40 mm Hg; P<0.01), without an increase in smooth muscle calcium (177±21 versus 201±16 nmol/L; P>0.05) or membrane depolarization (-38±4 versus -36±1 mV; P>0.05). In α-toxin-permeabilized vessels, MCAO caused increased sensitivity of the contractile apparatus to calcium. MCAO did not affect dilation to transient receptor potential melastanin receptor type 4 or protein kinase C inhibition but diminished dilation to Rho kinase inhibition. CONCLUSIONS The increased vasoconstriction of PAs during early postischemic reperfusion seems to be due to calcium sensitization of smooth muscle and could contribute to infarct expansion and limit neuroprotective agents from reaching their target tissue.

UI MeSH Term Description Entries
D008297 Male Males
D008564 Membrane Potentials The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization). Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009119 Muscle Contraction A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments. Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009131 Muscle, Smooth, Vascular The nonstriated involuntary muscle tissue of blood vessels. Vascular Smooth Muscle,Muscle, Vascular Smooth,Muscles, Vascular Smooth,Smooth Muscle, Vascular,Smooth Muscles, Vascular,Vascular Smooth Muscles
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002545 Brain Ischemia Localized reduction of blood flow to brain tissue due to arterial obstruction or systemic hypoperfusion. This frequently occurs in conjunction with brain hypoxia (HYPOXIA, BRAIN). Prolonged ischemia is associated with BRAIN INFARCTION. Cerebral Ischemia,Ischemic Encephalopathy,Encephalopathy, Ischemic,Ischemia, Cerebral,Brain Ischemias,Cerebral Ischemias,Ischemia, Brain,Ischemias, Cerebral,Ischemic Encephalopathies
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001160 Arterioles The smallest divisions of the arteries located between the muscular arteries and the capillaries. Arteriole
D014661 Vasoconstriction The physiological narrowing of BLOOD VESSELS by contraction of the VASCULAR SMOOTH MUSCLE. Vasoconstrictions
D015424 Reperfusion Restoration of blood supply to tissue which is ischemic due to decrease in normal blood supply. The decrease may result from any source including atherosclerotic obstruction, narrowing of the artery, or surgical clamping. It is primarily a procedure for treating infarction or other ischemia, by enabling viable ischemic tissue to recover, thus limiting further necrosis. However, it is thought that reperfusion can itself further damage the ischemic tissue, causing REPERFUSION INJURY. Reperfusions

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