Correspondence:
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Corresponding author: Agostino Gnasso, Department of Clinical and Experimental Medicine, University “Magna Graecia” Catanzaro, Viale Europa Localitá Germaneto 88100 Catanzaro, Italy. Tel.: +3909613647039; Fax: +3909613647250; E-mail: gnasso@unicz.it.
Abstract: BACKGROUND:The relationship between blood viscosity (BV) and endothelial function is rather complex. An increase in BV causes an increase in blood flow resistance, with negative hemodynamic effects; on the other hand, a moderate increase in BV causes an increase in wall stress shear (WSS), and consequent beneficial effects. As a matter of fact, the effect of changes in BV on endothelial function is not yet clear. OBJECTIVES:Aim of the present study was to evaluate in-vivo the effects of the acute reduction in BV on endothelial function, in healthy male subjects. METHODS:Fourteen healthy male blood donors were studied before and 48 hours after blood donation. Blood and plasma viscosity were measured at 37C° with a cone-plate viscometer. Endothelial function was evaluated through flow mediated vasodilation (FMD). RESULTS:Blood viscosity was reduced after blood donation (BV225 (cP) 4.53±0.59 vs.4.18±0.31, p < 0.05). FMD 50 s after cuff deflation was unchanged: 6.23±3.84 vs. 6.62±4.81, p = NS. The vasodilation, however, lasted longer and the area under the curve of FMD was significantly increased: 8.74±8.77 vs.16.14±8.65, p < 0.005. CONCLUSIONS:The present results demonstrate that the acute reduction of BV prolongs vasodilation, without affecting the amount of vasodilatation, possibly as adaptive reaction allowing more time for oxygen release.
