Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cardiovascular responses have been studied in baboons, after total exchange transfusion with hemoglobin solutions having various P50 values. At the end of the exchange transfusion, the hematocrit was 1.5%, the mean hemoglobin concentration was 4.4 g/dl, and the P50 varied between 12 and 26 mm Hg. Cardiac output did not change during the study, although heart rate increased, and stroke volume and MAP decreased. Hemoglobin concentration, per se, does not appear to be the critical stimulus for an increase in cardiac output with hemoglobin solution. In addition, the position of the hemoglobin-oxygen dissociation curve does not appear to influence these hemodynamic responses. The physiological response to anemia in the presence of hemoglobin solution appears different from that observed in the absence of plasma O2 carriers.
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PMID:Cardiac output response to extreme hemodilution with hemoglobin solutions of various P50 values. 11 94

Intramolecular crosslink of hemoglobin tetramers solved the problem of urine elimination and short intravascular retention time of cell free hemoglobin infusion. It also produced a family of crosslinked hemoglobins with P50 between 18 and 30 mmHg. However, it did not solve the problem of MAP increases in infused animals. It was proven that extravasation of hemoglobin into interstitial fluid was responsible for MAP increases. Extravasation and the MAP increase was avoided using a hemoglobin polymer with average size near 25 MDa. In spite of a very high oxygen affinity, this polymer delivered oxygen to tissues, producing either vasodilation or vasoconstriction according to oxygen needs. It was also proven that cell free hemoglobins are more efficient than red cells in delivering oxygen to tissues.
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PMID:Development of zero-link polymers of hemoglobin, which do not extravasate and do not induce pressure increases upon infusion. 1736 67

Microvascular responses to blood volume restitution using red blood cells (RBCs) with modified hemoglobin (Hb) oxygen affinity were studied in the hamster window chamber model during resuscitation from hemorrhagic shock. Allosteric effectors inositol hexaphosphate and 5-hydroxymethyl-2-furfural were introduced into the RBCs by electroporation to decrease and increase Hb-oxygen affinity. In vitro P50s (partial pressure of oxygen at 50% Hb saturation) were modified to 10 and 50 mmHg (normal P50, 32 mmHg). Awake hamsters were subjected to hemorrhage of 50% of blood volume, followed by a shock period of 1 h, and then resuscitated with 25% blood volume with high or low P50 RBCs (hematocrit, 50%). After resuscitation, base excess was significantly lower than baseline in the high-P50 RBC group (HP50; 0.3 +/- 2 vs. 5.0 +/- 1.7 mM) and MAP was lower than baseline in the low-P50 RBC group (LP50; 93 +/- 6 vs. 109 +/- 6 mM). Arteriolar diameter and flow were significantly lower in the HP50. Functional capillary density in the HP50 was significantly lower than LP50 at 60 and 90 min after resuscitation. There was no significantly difference in arteriolar PO2. Tissue PO2, venular PO2, and oxygen delivery were higher in LP50 than in HP50. There was no significant difference in oxygen extraction. Oxygen extraction ratio (oxygen extraction/oxygen delivery) x 100 was significantly higher in HP50 than in LP50. These results suggest that lowering blood P50 in resuscitation provides improved microvascular function in comparison with higher P50.
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PMID:Microcirculatory effects of changing blood hemoglobin oxygen affinity during hemorrhagic shock resuscitation in an experimental model. 1894 53

The effects of a polymerized bovine hemoglobin-based oxygen carrier (HBOC) and two derivatives on arteriolar vasoactivity and tissue oxygen tension were explored by administering HBOC in a dose-response fashion to normovolemic rats. The effect of oxygen affinity (P50) and viscosity was also explored, where the P50 and viscosity of the parent compound (HBOC-201) and its modifications (MP50 and LP50A) were as follows: 40mmHg and 3.0cP (HBOC-20l); 18mmHg and 4.4cP (MP50); and 17mmHg and 12.1cP (LP50A). Anesthetized male Sprague-Dawley rats (N=32) were randomized to receive one of the HBOC solutions, and were administered four infusions that increased in concentration for each dose (2, 22, 230 and 780mg/kg, IV). Data were compared to rats receiving an equivalent volume for each of the four infusions (0.4, 0.4, 3.8, 13.1ml/kg, IV) of iso-oncotic 5.9% human serum albumin (HSA). Increasing doses of either HBOC solutions or HSA were associated with increasing MAP. Doses 3 and 4 of HBOC-201, MP50 and HSA produced significant increases in MAP, whereas similar increases began at a lower dose (Dose 2) with LP50A. There were no significant changes in arteriolar diameters at any dose for any group. Interstitial partial pressure of oxygen (ISF PO2) remained unchanged for HBOC-201, MP50 and HSA, but LP50A caused a significant decrease in ISF PO2 compared to baseline after Doses 3 and 4. In conclusion, there was no evidence that HBOC-201 would perform better with increased oxygen affinity (40 to 18mmHg) or viscosity (3.0 to 4.4cP).
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PMID:Effects of a hemoglobin-based oxygen carrier (HBOC-201) and derivatives with altered oxygen affinity and viscosity on systemic and microcirculatory variables in a top-load rat model. 2504 29