Oxygen carrying capacity of completely artificial red blood cell substitute : Liposome-embedded-heme

A method for determining oxygen-carrying capacity of blood substitutes has been developed using the short-lived cyclotron-produced positron-emitting isotope 15O. This method measures the oxygen-carrying capacity of the blood substitutes in vivo in the presence of red blood cells and allows determination of changes in the oxygen-carrying capacity over time after exchange transfusion. This method is applied to the blood substitutes of liposome-encapsulated hemoglobin (LEH) and cell-free hemoglobin (Hb). We have used 15O (half-life of 2 min) to quantitate the lung uptake and tissue delivery of [15O2]LEH. Lung uptake studies were performed in intubated, catheterized rats after a 40% exchange transfusion of bovine LEH (LEBH; 0.68 g Hb/kg body wt), human hemolysate LEH (LEHH; 1.0 g Hb/kg body wt), or free bovine hemoglobin (SFHS; 0.56 g Hb/kg body wt). A bolus inhalation of 15O2 (3-5 mCi) was given at 15 min, 3 h, and 24 h post-transfusion. Arterial blood samples were collected, spun, and separated into LEH, red blood cell, and plasma fractions. 15O activity and hemoglobin content were determined for each fraction. Oxygen-carrying capacity was calculated as a percentage of the original red blood cell fraction removed. For LEBH, the carrying capacity was 15% at 15 min, 13% at 3 h, and 1% at 24 h. For LEHH, the carrying capacity was 30% at 15 min, 26% at 3 h, and 19% at 24 h. The marked decrease in carrying capacity at 24 h for LEBH compared with LEHH was attributable to the increased formation of methemoglobin in the circulating LEBH rather than increased removal from circulation, because total hemoglobin concentrations measured for both LEH samples decreased at a similar rate during the 24 h. The presence of methemoglobin reductase and other naturally occurring antioxidants in the LEHH may be responsible for maintaining the higher levels of oxyhemoglobin. Oxygen-carrying capacity for SFHS also decreased over time but at a much sharper rate compared with both LEH formulations. The carrying capacity for SFHS of 8% measured at 15 min decreased to 0.3% at 3 h and undetectable levels at 24 h. This sharper decrease in carrying capacity for SFHS is attributable to the rapid removal of the hemoglobin from circulation.d

Download Full-text

Erythropoietin in Brain Development and Beyond

Anatomy Research International ◽

10.1155/2012/953264 ◽

2012 ◽

Vol 2012 ◽

pp. 1-15 ◽

Cited By ~ 18

Author(s):

Mawadda Alnaeeli ◽

Li Wang ◽

Barbora Piknova ◽

Heather Rogers ◽

Xiaoxia Li ◽

...

Keyword(s):

Blood Cell ◽

Red Blood Cell ◽

Cell Types ◽

Erythropoietin Receptor ◽

Adult Brain ◽

Receptor Expression ◽

Neural Cells ◽

Erythroid Progenitor ◽

Cell Production ◽

Oxygen Carrying Capacity

Erythropoietin is known as the requisite cytokine for red blood cell production. Its receptor, expressed at a high level on erythroid progenitor/precursor cells, is also found on endothelial, neural, and other cell types. Erythropoietin and erythropoietin receptor expression in the developing and adult brain suggest their possible involvement in neurodevelopment and neuroprotection. During ischemic stress, erythropoietin, which is hypoxia inducible, can contribute to brain homeostasis by increasing red blood cell production to increase the blood oxygen carrying capacity, stimulate nitric oxide production to modulate blood flow and contribute to the neurovascular response, or act directly on neural cells to provide neuroprotection as demonstrated in culture and animal models. Clinical studies of erythropoietin treatment in stroke and other diseases provide insight on safety and potential adverse effects and underscore the potential pleiotropic activity of erythropoietin. Herein, we summarize the roles of EPO and its receptor in the developing and adult brain during health and disease, providing first a brief overview of the well-established EPO biology and signaling, its hypoxic regulation, and role in erythropoiesis.

Download Full-text

Microvascular responses to hemodilution with Hb vesicles as red blood cell substitutes: influence of O2 affinity

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1999.276.2.h553 ◽

1999 ◽

Vol 276 (2) ◽

pp. H553-H562 ◽

Cited By ~ 32

Author(s):

Hiromi Sakai ◽

Amy G. Tsai ◽

Ronald J. Rohlfs ◽

Hiroyuki Hara ◽

Shinji Takeoka ◽

...

Keyword(s):

Blood Cell ◽

Red Blood Cell ◽

Carrying Capacity ◽

Capillary Density ◽

Microvascular Perfusion ◽

Phospholipid Vesicles ◽

Molar Ratios ◽

Allosteric Effector ◽

Syrian Golden Hamsters ◽

Optimal Value

Phospholipid vesicles encapsulating purified hemoglobin (HbV) were developed to provide O2-carrying capacity to plasma expanders. Microvascular perfusion was determined for HbV with different O2 affinity (P50 = 9, 16, and 30 mmHg) prepared by coencapsulating pyridoxal 5′-phosphate (PLP) at the molar ratios of [PLP]/[Hb] = 0, 0.5, and 3, respectively (cf. hamster blood, P50: 28 mmHg), and suspended in 8 g/dl human serum albumin (HSA). Eighty percent of the red blood cell (RBC) mass of conscious Syrian golden hamsters fitted with dorsal skinfold windows was substituted with either of the HbV-HSA suspensions, washed hamster RBC suspended in HSA (RBC-HSA), and HSA alone. All three HbV-HSA groups and RBC-HSA groups showed stable blood pressure and heart rate, which could not be sustained with HSA alone. Only the HbV (P50 = 9)-HSA group showed an increase in arterial O2tension (89.8 ± 14.7 mmHg, baseline 58.4 ± 4.0 mmHg) because of hyperventilation, and microvascular perfusion was decreased, indicating that facilitated O2 unloading of HbV by decreasing the O2 affinity (increasing P50) with PLP as an allosteric effector is important. Microvascular perfusion and microvascular and interstitial O2tensions in the HbV (P50 = 16 and 30)-HSA groups were significantly higher than those in the HSA group. The O2 release rate from the HbV was 18–32 s−1 vs. 4.4 s−1 for RBC. Functional capillary density was improved from 17 to 41% on average by decreasing P50 from 30 to 16 mmHg, which appears to be an optimal value for the P50 in this system.

Download Full-text

Haemoglobin H+ equilibria in lamprey (Lampetra fluviatilis) and hagfish (Myxine glutinosa)

Journal of Experimental Biology ◽

10.1242/jeb.202.14.1963 ◽

1999 ◽

Vol 202 (14) ◽

pp. 1963-1968

Author(s):

F.B. Jensen

Keyword(s):

Blood Cell ◽

Red Blood Cell ◽

Carrying Capacity ◽

Venous Blood ◽

Evolutionary Divergence ◽

High Concentration ◽

High Co2 ◽

Virtual Absence ◽

Fixed Acid ◽

Haldane Effect

Agnathans, comprising lamprey and hagfish species, have been reported to be practically devoid of HCO3-/Cl- exchange across the red blood cell membrane. This suggests that the capacity of their haemoglobin (Hb) to remove H+ is essential for obtaining a high CO2-carrying capacity in the blood. Hydrogen ion titrations were performed on oxygenated and deoxygenated composite Hbs from river lamprey and from Atlantic hagfish at 15 degrees C and an ionic strength of 0.1 (0.1 mol l-1 KCl). Lamprey Hb was characterised by very low buffer values when the degree of oxygenation was constant, whereas the fixed-acid Haldane effect was large (uptake of approximately 0.9 H+ per monomer upon deoxygenation). Hagfish Hb, in contrast, had large buffer values and a moderate fixed-acid Haldane effect. In deoxygenated Hb, the low buffer values in lamprey correlated with the presence of only 1–1.5 titratable ‘neutral’ groups (normally histidines and α -amino groups) per monomer, whereas there were 4–5 titratable ‘neutral’ groups per monomer in hagfish. The large differences in Hb/H+ equilibria between the two species reflect the early evolutionary divergence between lampreys and hagfish. With respect to CO2 transport, the special Hb/H+ equilibria and the high red blood cell pH in lamprey ensure a high concentration of free HCO3- inside the red cells in venous blood, which compensates for the absence of a shift of HCO3- to the plasma. The Hb/H+ equilibria in hagfish are less effective in ensuring a high CO2-carrying capacity given the virtual absence of a red blood cell HCO3-/Cl- exchange, and other adaptations may be involved.

Download Full-text

Control and coordination of gas transfer in fishes

Canadian Journal of Zoology ◽

10.1139/z89-419 ◽

1989 ◽

Vol 67 (12) ◽

pp. 2961-2970 ◽

Cited By ~ 99

Author(s):

Steve F. Perry ◽

Chris M. Wood

Keyword(s):

Blood Cell ◽

Oxygen Content ◽

Red Blood Cell ◽

Carrying Capacity ◽

Blood Cells ◽

Gas Transfer ◽

Blood Oxygen ◽

Acid Base ◽

Acid Base Status ◽

Periods Of Stress

Recent developments pertaining to the control and coordination of gas transfer in fishes have been reviewed. Gill ventilatory water flow can markedly affect blood respiratory and blood acid–base status. Although arterial oxygen content traditionally has been considered the predominant factor controlling ventilation, we present evidence for additional involvement of both blood acid–base status and circulating catecholamines. An analysis of the independent effects of blood oxygen content, acid–base status, and catecholamines in controlling ventilation is confounded by the interrelationships among these variables. It is likely, however, that each factor is involved to some extent in ventilatory control in fishes. Blood oxygen transport is affected by the carrying capacity of the blood and red blood cell chemical status. Blood oxygen-carrying capacity is increased during periods of stress by adrenergic release of red blood cells from the spleen. Concurrently, adrenergic stimulation of red blood cell Na+–H+ exchange, reduction of intracellular nucleoside triphosphates, swelling of red blood cells, and respiratory alkalosis all tend to increase oxygen affinity and capacity of hemoglobin. Results of recent in vivo studies indicate that adrenergic inhibition of plasma bicarbonate dehydration may contribute to the respiratory acidosis after exhaustive exercise in fishes. Evidence is presented to show that hypoxemia, rather than blood acidosis per se, is the proximate stimulus for catecholamine mobilization during periods of stress in fishes.

Download Full-text