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Blood constituents

Blood constituents. -Erythrocytes (red blood cells) -Leukocytes (white blood cells) -Thrombocytes (platelets) -Plasma (55-60% of volume): a). water (90-91%) b). proteins (6.5-8.5%) c). electrolytes, anions, etc. Determinants of blood viscosity. RBC concentration (hematocrit)

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Blood constituents

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  1. Blood constituents -Erythrocytes (red blood cells) -Leukocytes (white blood cells) -Thrombocytes (platelets) -Plasma (55-60% of volume): a). water (90-91%) b). proteins (6.5-8.5%) c). electrolytes, anions, etc.

  2. Determinants of blood viscosity • RBC concentration (hematocrit) • Plasma viscosity (Newtonian fluid) • RBC deformability (at high hear rates) • RBC aggregation (at low hear rates)

  3. Normal (deformable) RBCs Dr. Max Hardeman, with permission Roggenkamp, et al., 1986

  4. Pathologies related to significantly increased RBC aggregation • Cardiovascular diseases • Diabetes • Obesity • Hypertension • Atherosclerosis • Shock

  5. Methods of evaluation • Blood viscosity (viscometers; rheometers) • RBC deformability (asymptotic blood viscosity; ektacytometry) • RBC aggregation (low shear blood viscosity, erythrocyte sedimentation rate, aggregometers) Results obtained by the most of these methods strongly depend on hematocrit

  6. Ratio of male to female mortality due to myocardial infarction, IHD, and cancer (Vital Statistics of the US)

  7. Hypotheses • The higher level of the circulating ovarian hormones (estrogens) that produce a vasodilatory effect mediated by NO on coronary arteries protect women of reproductive age (however, the increase in risk of heart disease was found to be essentially the same in women with surgically induced menopause regardless of ovary removal) • Our hypothesis was that rheological properties of the premenopausal female blood are optimized by a monthly blood loss to maximize gas transport

  8. Correlation between hematocrit and blood pressureStudy of a large group of 17-18 years old teenagers (756 males and 705 females)

  9. Number of teenagers with elevated blood pressure (above 140/85 mm Hg) Males Females

  10. Number of teenagers with elevated hematocrit (Ht>50%) in the hypertensive groups Males Females

  11. Effect of hematocrit on blood viscosity20% difference in Ht causes ~90% and ~40% difference in low and high shear viscosity

  12. Large arteries and braches Small arteries Aorta Arterioles Capillaries Fåhraeus and Fåhraeus-Lindquist effectsReduction of RBC concentration and apparent viscosity in microvessels (less than 0.5 mm diameter) due to development of the near-wall cell free layer and “plasma skimming” effect. The plasma layer increases the resistance for O2 diffusion and decreases vessel wall shear stresses.

  13. RBC age distribution in male and female blood Females Males The picture is based on data published by Micheli et al. , 1984

  14. RBCs Centrifuged Centrifuged Whole blood Young RBCs Plasma RBCs Old RBCs

  15. Mechanical properties of old and young red blood cells RBCDeformability RBC Sedimentation Rate p<0.001 p<0.001 p<0.05 p<0.05 Difference (%) Low Shear Viscosity RBC Mechanical Fragility

  16. Rheological parameters in male and premenopausal female blood

  17. Oxygen Delivery Index (hematocrit/blood viscosity ) p<0.001 Oxygen Delivery Index

  18. Asymptotic blood viscosity and oxygen delivery index (ODI) vs. hematocrit for pre-menopausal women (n=47) and age-matched men (n=50)

  19. Oxygen Delivery Index in premenopausal women, men and cardiac patients

  20. Summary • Male blood has higher viscosity due to higher hematocrit and RBC aggregation and lower RBC deformability • Men possess a higher number of old RBCs and a fewer number of young RBCs than premenopausal women • Old RBCs demonstrate an increased ability to aggregate and decreased deformability as compared to young RBCs • Oxygen delivery index is significantly lower (p<0.001) for male blood than for blood of pre-menopausal females

  21. Summary (cont.) • Increased blood viscosity and aggregability of RBCs and decreased deformability of RBCs are known risk factors of cardiovascular diseases. • The difference in the mechanical properties of male and female blood places men at higher risk of cardiovascular diseases than pre-menopausal women • Blood donation or regular, small phlebotomy might help to improve rheological properties of blood and reduce the risk of cardiovascular diseases in men and post-menopausal women

  22. RBC aggregation promotes a formation of the near-wall plasma layer in microvessels reducing wall shear stresses, shear-induced vasodilation and intracapillary hematocrit. Due to exercises, increased blood flow decreases RBC aggregation and, thus, reduces the near wall plasma layer and plasma skimming at bifurcations. This leads to an increase in wall shear stresses, vasodilation, number of functioning capillaries, and concentration of RBCs in capillaries enhancing delivery of O2 and removal of metabolites. tw tw Effect of exercises on RBC aggregation and microcirculation

  23. References • Micheli V, Taddeo A, Vanni AL, Pecciarini L, Massone M and Ricci MG. Distribuzione in gradiente di densita’ degli eritrociti umani: differenze lagate al sesso, Boll. Soc. Italiana Biol. Speriment. LX(3) (1984), 665–671. • Kameneva MV and Timofeev VF. Increased hematocrit as a risk factor for arterial hypertension. Cardiologiya 10 (1986), 105–106. • Lowe GDO, editor. Clinical Blood Rheology. CRC Press, Boca Raton, Florida, 1988. • Vital Statistics of the United States 1990, Vol. 2, Mortality, U.S. Department of Health and Human Services, Hyattsville, MD, 1994. • Kameneva MV. Effect of hematocrit on the development and consequences of some hemodynamic disorders. In: "Contemporary Problems of Biomechanics," GG Chernyi and SA Regirer, (eds.). Mir. Publ., Moscow, USSR, CRC Press, Boca Raton, 1990, 111-26. • Meyers DC, Strickland D, Maloley PA, Seburg JJ, Wilson JE and McManus BF. Possible association of a reduction in cardiovascular events with blood donation, Heart 78(2) (1997), 188–193. • Kameneva MV, Garrett KO, Watach MJ, and Borovetz HS. Red blood cell aging and risk of cardiovascular diseases. Clinical Hemorheology and Microcirculation, 18(1):67-74, 1998. • Kameneva MV, Watach MJ, and Borovetz HS. Gender difference in rheologic properties of blood and risk of cardiovascular diseases. Clinical Hemorheology and Microcirculation, 21(3-4):357-363, 1999. • Kameneva MV, Watach MJ, and Borovetz HS. Rheologic dissimilarities in female and male blood: potential link to development of cardiovascular diseases. In: Advances in Experimental Medicine & Biology. Oxygen Transport to Tissue XXIV. JF Dunn and HM Swartz (Eds.), Kluwer Academic/Plenum Publisher, New York, 2003, vol. 530, pp 689-696.

  24. Thank you!

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