Activation of N-methyl D-aspartate (NMDA) receptors has no influence on rheological properties of erythrocytes.
OBJECTIVE
Red blood cells (RBCs) express N-methyl D-aspartate (NMDA) receptors on their surface. We tested if NMDA receptor activation or inhibition had an influence on RBC deformability and aggregability.


METHODS
Heparinized blood was drawn from healthy volunteers and centrifuged. RBCs were washed twice and resuspended with a hematocrit of 30% in a same buffer solution containing 3% dextran 70. Aliquots were prepared: a) control; b) containing 100 μM homocysteic acid (NMDA receptor agonist); c) 100 μM memantine (NMDA receptor inhibitor) and 100 μM homocysteic acid. RBC suspension viscometry (Contraves LS-30) was done at 37 °C with shear rates of 37.6 s(-1) and 0.1 s(-1). RBC aggregability was assessed with a Myrenne aggrometer and sedimentation rate.


RESULTS
Neither NMDA receptor activation nor inhibition had an influence on biophysical properties of RBCs. RBC suspension viscosity at a shear rate of 37.6 s(-1) was 3.62 ± 0.16, 3.61 ± 0.13, and 3.62 ± 0.16 mPa.s for control, homocysteic acid, and memantine + homocysteic acid, respectively, indicating an unchanged RBC deformability. The RBC aggregability parameters (low shear viscosity, Myrenne aggregometry at stasis (M) and 3 s(-1) (M1), and the sedimentation rate) showed no influence of either memantine and/or homocysteic acid. A large interindividual variability in RBC aggregability was observed. A good correlation was found between M, M1 and sedimentation values, but not with low shear viscosity values.


CONCLUSIONS
An activation or inhibition of NMDA receptors on RBCs has no influence on their deformability and aggregability. RBC aggregability varies largely among individuals, which was consistently detected by the sedimentation rate and the Myrenne aggregometer, but not by low shear viscosity, which should not be used for this purpose.
Department of Internal Medicine, Kantonsspital Graubünden, Chur, Switzerland. walter.reinhart@ksgr.ch
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Reinhart
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Geissmann-Ott
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Bogdanova
D001799:Blood Sedimentation / Q000187:drug effects*; D020013:Calcium Signaling / Q000187:drug effects; D004903:Erythrocyte Aggregation / Q000187:drug effects*; D004907:Erythrocyte Deformability / Q000187:drug effects*; D004912:Erythrocytes / Q000187:drug effects*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006710:Homocysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D007206:Individuality; D017136:Ion Transport / Q000187:drug effects; D008559:Memantine / Q000494:pharmacology; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists* / Q000097:blood; D033081:Shear Strength; D013535:Suspensions; D014783:Viscosity
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D013535:Suspensions; D006710:Homocysteine; C007956:homocysteic acid; D008559:Memantine