Microvascular responses to hemodilution with Hb vesicles as red blood cell substitutes: influence of O 2 affinity
Phospholipid vesicles encapsulating purified hemoglobin (HbV) were developed to provide O -carrying capacity to plasma expanders. Microvascular perfusion was determined for HbV with different O affinity (P = 9, 16, and 30 mmHg) prepared by coencapsulating pyridoxal 5'-phosphate (PLP) at the mol...
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Published in | American journal of physiology. Heart and circulatory physiology Vol. 276; no. 2; pp. H553 - H562 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
01.02.1999
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Subjects | |
Online Access | Get full text |
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Summary: | Phospholipid vesicles encapsulating purified hemoglobin (HbV) were developed to provide O
-carrying capacity to plasma expanders. Microvascular perfusion was determined for HbV with different O
affinity (P
= 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, P
: 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 (P
= 9)-HSA group showed an increase in arterial O
tension (89.8 ± 14.7 mmHg, baseline 58.4 ± 4.0 mmHg) because of hyperventilation, and microvascular perfusion was decreased, indicating that facilitated O
unloading of HbV by decreasing the O
affinity (increasing P
) with PLP as an allosteric effector is important. Microvascular perfusion and microvascular and interstitial O
tensions in the HbV (P
= 16 and 30)-HSA groups were significantly higher than those in the HSA group. The O
release rate from the HbV was 18-32 s
vs. 4.4 s
for RBC. Functional capillary density was improved from 17 to 41% on average by decreasing P
from 30 to 16 mmHg, which appears to be an optimal value for the P
in this system. |
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ISSN: | 0363-6135 1522-1539 |
DOI: | 10.1152/ajpheart.1999.276.2.H553 |