The role of facilitated diffusion in oxygen transport by cell-free hemoglobins: implications for the design of hemoglobin-based oxygen carriers.
We compared rates of oxygen transport in an in vitro capillary system using red blood cells (RBCs) and cell-free hemoglobins. The axial PO(2) drop down the capillary was calculated using finite-element analysis. RBCs, unmodified hemoglobin (HbA(0)), cross-linked hemoglobin (alpha alpha-Hb) and hemoglobin conjugated to polyethylene-glycol (PEG-Hb) were evaluated. According to their fractional saturation curves, PEG-Hb showed the least desaturation down the capillary, which most closely matched the RBCs; HbA(0) and alpha alpha-Hb showed much greater desaturation. A lumped diffusion parameter, K*, was calculated based on the Fick diffusion equation with a term for facilitated diffusion. The overall rates of oxygen transfer are consistent with hemoglobin diffusion rates according to the Stokes-Einstein Law and with previously measured blood pressure responses in rats. This study provides a conceptual framework for the design of a 'blood substitute' based on mimicking O(2) transport by RBCs to prevent autoregulatory changes in blood flow and pressure.
McCarthy
M R
MR
Department of Bioengineering, University of California, San Diego, 92161, USA.
Vandegriff
K D
KD
Winslow
R M
RM
D000465:Algorithms; D001693:Biological Transport, Active; D001802:Blood Substitutes / Q000737:chemistry / Q000378:metabolism*; D002196:Capillaries / Q000502:physiology; D002474:Cell-Free System; D004058:Diffusion; D015195:Drug Design; D020342:Finite Element Analysis; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008954:Models, Biological; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D011092:Polyethylene Glycols / Q000737:chemistry
D001802:Blood Substitutes; D006454:Hemoglobins; D011092:Polyethylene Glycols; D010100:Oxygen