Microhemodynamics after Infusion of an Artificial O_2 Carriers Using Laser Flash Irradiation.

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(1)Hemoglobin-vesicles (HbV) has been developed to substitute the function of RBCs. We developed new methods to analyze the microhemodynamics after infusion of HbV into rodents, and evaluated the safety and efficacy of HbV. Fluorescence-labeled HbV was infused into hamsters and the liver was observed in situ with a laser con focal microscopy. This allowed visualization of HbV flowing in the sinusoid, and the particles were finally captured and accumulated in the Kupffer cells, which could be observed as intensified fluorescence. Histopathological analysis using anti-human Hb antibody and serum clinical chemistry demonstrated the prompt metabolism and excretion of HbV without any irreversible changes.(2)Capillary RBC flow in the skin of rat tail during an extreme hemodilution with albumin was microscopically observed with a noninvasive transcutaneous technique using flash epi-illumination. The RBC flow rates monotonously increased up to 294 ± 110% of the basal value at the 60% level of … More blood exchange, which was in contrast to the abdominal aortic blood flow increase to 148 ± 20%. Capillary hematocrit did not appear to fall in the same proportion as the systemic hematocrit, which coincided with the previous observations. These results indicate that microhemodynamic properties during hemodilution can be transcutaneously analyzed with this new technique without surgical preparation of the skin.(3)The O_2 release from flowing HbVs was examined using an O_2-permeable polymer tube (inner diameter, 28 μm) exposed to a deoxygenated environment. Measurement of O_2 release was performed using an apparatus that consisted of an inverted microscope and a scanning-grating spectrophotometer with a photon-count detector, and the rate of O_2 release was determined based on the visible absorption spectrum in the Q band of Hb. The rate of O_2 release from the HbV/RBC mixtures was similar to that of RBCs alone. On the other hand, the addition of acellular Hb solution to RBCs significantly enhanced the rate of deoxygenation. This should mainly be due to the difference in the particle size (250 vs. 7 nm) that affects their diffusion for the facilitated O_2 transport. Less