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  • Title: PDGF-induced coupling of function with metabolism in microvascular pericytes of the retina.
    Author: Sakagami K, Kodama T, Puro DG.
    Journal: Invest Ophthalmol Vis Sci; 2001 Jul; 42(8):1939-44. PubMed ID: 11431464.
    Abstract:
    PURPOSE: The aim of this study was to test the hypothesis that platelet-derived growth factor (PDGF)-BB regulates the physiology of retinal pericytes, which are contractile cells located on the abluminal surface of capillaries. The expression of PDGF-BB and its cognate receptor in retinal vessels suggests a vasoactive function. However, although endothelium-derived PDGF-BB appears vital for the development of pericyte-containing microvessels, its role in the mature vasculature remains uncertain. METHODS: Based on the premise that ion channels mediate the responses of pericytes to vasoactive signals, the perforated-patch configuration of the patch-clamp technique was used to determine the effect of PDGF-BB on the ionic currents and membrane potential of pericytes located on microvessels freshly isolated from the adult rat retina. Changes in pericyte calcium levels were monitored with the calcium indicator fluo-4. Differential interference contrast optics and image analysis software aided in assessing the effects of PDGF-BB on the lumens of isolated pericyte-containing microvessels. In some experiments, blockers of adenosine triphosphate (ATP) synthesis created chemical ischemia. RESULTS: Electrophysiological recordings from pericytes showed that PDGF-BB can activate nonspecific cation channels, chloride channels, and ATP-sensitive potassium channels. The metabolic status of an isolated capillary determined which of these ion channels were activated by PDGF-BB and thereby whether the membrane potential decreased or increased, the cell calcium rose or fell, and the vessel lumen constricted or dilated. CONCLUSIONS: The ability of PDGF-BB to be a vasoconstrictor when energy supplies are ample and to be a vasodilator under ischemic conditions may provide an efficient mechanism to link capillary function to local metabolic needs.
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