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


OBJECTIVE
To 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).


METHODS
Single pericytes were loaded with 2 micromol/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 micromol/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.


RESULTS
Basal [Ca2+] 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.


CONCLUSIONS
Single 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.
Skinner
S
S
University Hospital, Zürich, Switzerland.
Niederer
E
E
Locher
R
R
Vetter
W
W
D000818:Animals; D001161:Arteriosclerosis / Q000209:etiology; D001794:Blood Pressure / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006973:Hypertension / Q000209:etiology; D066298:In Vitro Techniques; D008077:Lipoproteins, LDL / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D012160:Retina / Q000166:cytology
D008077:Lipoproteins, LDL; D002118:Calcium