Single pericytes and pericytes in suspension are stimulated in a similar way by low-density lipoprotein

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BackgroundPericytes are regarded as the microvascular counterpart of smooth muscle cells and implicated in the regulation of blood pressure at the microvascular level. Ca2+ plays an important role in biochemical processes involved in blood pressure regulation and can be activated by low-density lipoprotein (LDL) cholesterol.ObjectiveTo determine whether stimulation either of single cells or of cells in suspension by LDL would produce any difference in the increase in cytosolic free calcium levels ([Ca2+]i).Design and methodsSingle pericytes were loaded with 2 μmol/l of the Ca2+-sensitive dye Indo-1/AM. The Indo-1 fluorescence was recorded at 405 nm (Ca2+-bound) and 485 nm (Ca2+-free) after stimulation with LDL. Pericytes in suspension were loaded with 2 μmol/l of the Ca2+-sensitive dye FURA-2/AM. The FURA-2 fluorescence kinetics were recorded at 340–380 nm. Ratios of fluorescence at the two wavelengths were transformed to [Ca2+]i.ResultsBasal [Ca2+]i levels appeared to be higher in single cells (148 ± 13 nmol/l, n = 20) than they were in cells in suspension (128 ± 8 nmol/l, n = 25; P = 0.0078). After stimulation with LDL the increase in [Ca2+]i in both systems was about 220% above baseline. A clear dose dependency was seen for both systems.ConclusionsSingle pericytes and pericytes in suspension increase their [Ca2+]i after stimulation with LDL dose-dependently. Even though single-cell measurements revealed some technical limitations, their responses were comparable to those obtained in a cell suspension. In analogy to aortic smooth muscle cells, our results indicate that LDL might also play a blood-pressure-regulatory role in the microvasculature.

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