Barbara Urbaitis

Role of Nitric Oxide Scavenging in Peripheral Vasoconstrictor Response to ββ Cross-Linked Hemoglobin

Transfusion with many crosslinked hemoglobin solutions causes an increase in arterial pressure that may be mediated by scavenging of nitric oxide (NO). If so, we postulated that inhibiting synthesis of NO after hemoglobin transfusion would fail to cause vasoconstriction ordinarily seen with such inhibition. In pentobarbital anesthetized cats, we tested whether administration of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), produced peripheral vasoconstriction after isovolemic exchange transfusion with hemoglobin to the same extent as occurs with L-NAME infusion in time controls and in controls matched for reduced hematocrit (17%) with albumin transfusion. Bovine hemoglobin was treated aerobically with bis-(3,5-dibromosalicyl) fumarate to produce βbeta;-81 lysine crosslinks. Hemoglobin exchange transfusion increased mean arterial blood pressure and there was no further increase after L-NAME. In contrast, L-NAME increased pressure in the time controls and albumin controls. Hemoglobin...

Immobilized hemoglobin in the purification of hemoglobin-based oxygen carriers

Chemically modified hemoglobins can be used as oxygen carriers in cell-free fluids provided that they have a low oxygen affinity and are stable towards dissociation into subunits. The latter species are undesirable because they are filtered rapidly through the kidneys, have renal toxicity and are characterized by a high oxygen affinity. A most important step in the preparation of hemoglobin-based oxygen carriers is therefore their purification from any dissociable material. Hemoglobin immobilized as alpha beta dimers on Sepharose lends itself naturally to this purpose as it is able to interact in a specific and reversible way with soluble alpha beta dimers. Hemoglobin affinity columns are very effective in the purification of cross-linked and pseudo-cross-linked human and bovine hemoglobin. The applicability of the technique is enhanced by the ease with which alpha beta dimers from different species cross-interact to yield hybrid alpha 2 beta 2 tetramers. It is shown that hemoglobin affinity columns may provide analytical information on the cross-linking reaction itself.

Hemoglobin tetramers stabilized with polyaspirins.

Organic acids activated by esterification with 3,5-dibromosalicylate react preferentially either with the beta 82 lysines or the alpha 99 lysines of hemoglobin. The versatility and site specificity of these polysapirins and the usage of both human and bovine hemoglobins allowed the construction of a family of oxygen carriers with various P50 ranging from 10 to 50 mmHg. These derivatives are obtained in pure homogeneous form by column chromatography. They are stabilized tetramers where the dissociation into dimers is inhibited. The latest addition is Tri-(3,5,dibromosalicyl)-benzenetricarboxylate, which crosslinks both human and bovine hemoglobin across the beta subunits, decreasing the oxygen affinity of both proteins. The crosslinked hemoglobins have a normal Bohr effect, more expanded in the alkaline region, and are sensitive to chlorides but not to polyphosphates. Solutions of stabilized tetramers, infused into rats or cats up to 25-50% blood replacement, do not produce altered renal and cardiac function. In the cat isovolemic hemodilution increases cerebral flow in controls treated with albumin solutions, when an oxygen carrier is used the cerebral flow remains normal.

Effect of Ischemia and Hypertonic Saline Loading on Renal Adenine Nucleotides

The present study was done to determine: (1) regional (cortex, red medulla and papilla) changes in ATP, ADP and AMP resulting from periods of ischemia of 30-300 s; (2) whether ischemic changes in aden

Renal excretion of pseudo-cross-linked human, porcine and bovine hemoglobins

UNLABELLED The present experiments were done to determine plasma retention, urinary excretion, and acute renal effects of bolus administration (20 mg/100 g), of hemoglobins (human, bovine and porcine) whose tetrameric structure was stabilized by a pseudo-cross-link between the beta-chains. Standard renal clearance studies showed that these preparations had no immediate adverse effects on GFR or ERPF, however, urine flow and electrolyte excretion commonly increased. Plasma disappearance curves best fit a double-exponential and showed components with half-times of 28 +/- 3 and 257 +/- 43 min. A variable fraction, 57 +/- 6%, appeared in the urine, in phase with the early-fast component of plasma disappearance. This in vivo finding of extensive urinary excretion conflicted with sedimentation velocity analysis of these preparations which indicated a homogenous preparation with mean molecular weight of a stable and therefore, unfilterable tetramer. It appears that the glomerular filter selects for permeant species not easily detected by sedimentation velocity analysis. The different species may reflect the presence, within the PXLs of conformational-slow-equilibria among isomeric forms with different degrees of filterability. IN CONCLUSION It is important, useful and simple to determine urinary excretion as a means to ascertain molecular stability in vivo.

Effect of Fructose and Mannitol on Dog Renal Cortical Adenine Nucleotide Content, in vivo

The renal cortex of anesthetized dogs was found to contain per gram lyophilized dry weight 9.5+/-0.6 micronmol ATP, 3.2+/-0.5 MICRONMOL ADP, 0.68+/-0.3 MICRONMOL AMP, and 22.5+/-4.4 micronmol Pi. These amounts were unchanged by the administration of moderate amounts of saline or hypertonic mannitol in load doses of about 20mmol/kg. Fructose in doses of 5 mmol/kg was found to cause a marked decrease in cortical ATP content. In doses of 20 mmol/kg fructose not only caused a decrease in ATP, but in total adenine nucleotides and Pi content as well. These results are consistent with the mode of action proposed for fructose, in rat kidney.