Hyperthermia, unlike ionizing radiation and chemical oxidative stress, does not stimulate proteolysis in erythrocytes

Indicators of erythrocyte damage after microwave warming of packed red blood cells

BACKGROUND

Localized overheating of packed red blood cells (PRBCs) after microwave warming with consequent damage to erythrocytes has been reported. We therefore compared possible cellular markers of erythrocyte damage, as measured by flow cytometry, with laboratory indicators of hemolysis to evaluate the effects of microwave warming on PRBCs.

METHODS

PRBC samples were warmed to room temperature or to 37, 42, 47, 52, or 57 degrees C in a water bath. Flow cytometry was performed after fluorescein labeling using antibodies to spectrin, Ca(2+)-ATPase, and Na(+)-K(+)-ATPase. The forward-to-sideward scatter (FSC/SSC) ratio and antibody binding were evaluated. Plasma free hemoglobin (FHb) and alpha-hydroxybutyrate dehydrogenase (HBDH) were measured immediately after heating and after 48 h. In addition, all measurements were made before and after the heating of PRBCs to 35 degrees C by a microwave blood warmer.

RESULTS

Analysis of 15000 erythrocytes showed a decrease in the FSC/SSC ratio and antibody binding above 47 degrees C [at 37 degrees C, median (SD) of 94.2 (7.4) with 0.07 (0.05)% fluorescein-positive; at 52 degrees C, median (SD) of 177.0 (19.0) with 18.5 (6.4)% positively gated; P <0.001]. FHb [room temperature, 0.3 (0.2) g/L] was increased 2-fold at 37 and 42 degrees C, 4-fold at 47 degrees C, and 25-fold at 52 degrees C. HBDH increased in parallel. Hemolysis markers showed an additional twofold increase 48 h after heating to 42 and 47 degrees C. Microwave heating to 35 degrees C did not produce significant changes of any marker.

CONCLUSIONS

All markers of cellular damage were altered after heating to >47 degrees C, and a substantial part of hemolysis was delayed. The methodology can be used for future testing of other blood warming devices.

The effects of some antibiotics on sheep lens glucose 6-phosphate dehydrogenase in vitro

PURPOSE

To investigate the in vitro effects of gentamicin sulfate, vancomycin hydrochloride, sodium cefazolin and ceftriaxone on glucose 6-phosphate dehydrogenase enzyme (G6PD) purified from sheep lenses.

METHODS

G6PD was purified from sheep lenses with a yield of 66.8% and a specific activity of 7.8 U/mg proteins, and 10,400-fold using ammonium sulfate fractionation and 2',5'-ADP Sepharose 4B affinity gel. The enzyme activity was determined by Beutler's method.

RESULTS

Gentamicin sulfate and vancomycin hydrochloride strongly inhibited the enzyme in vitro. The concentrations causing 50% inhibition (IC50 were 15.34, and 8.0 mM, respectively. Conversely, cefazolin sodium strongly activated this enzyme, and ceftriaxone caused milder activation.

CONCLUSIONS

If a patient with G6PD deficiency requires gentamicin sulfate or vancomycin hydrochloride, routine ophthalmic did not inhibit this enzyme. Postmortem studies are now needed to investigate the activity of G6PD and how it is affected by these antibiotics.

Effects of metamizol and magnesium sulfate on enzyme activity of glucose 6-phosphate dehydrogenase from human erythrocyte in vitro and rat erythrocyte in vivo

OBJECTIVE

Effects of metamizol and magnesium sulfate on erythrocyte glucose 6-phosphate dehydrogenase enzyme activity were investigated in in vitro and in vivo conditions.

METHODS

For in vitro studies, glucose 6-phosphate dehydrogenase was purified from human erythrocyte and rats were used for in vivo studies. Enzyme activity was determined according to the Beutler method by using a spectrophotometer at 340 nm.

RESULTS

The results of in vitro study showed that their mean K(i) values were 6.35 x 10(-3) M for metamizol and 1.32 x 10(-2) M for magnesium sulfate and their inhibition types were uncompetitive. I(50) value was 17 mM for metamizol and 50 mM for magnesium sulfate in in vitro study. In the case of in vivo studies, 200 mg/kg metamizol inhibited the enzyme activity by 40% during the first 1.5 h (p < 0.05), and 225 mg/kg magnesium sulfate significantly inhibited the enzyme activity throughout 24 h (p < 0.01).

CONCLUSION

The results of this study suggested that metamizol and magnesium sulfate have significant inhibition effect on the activity of glucose 6-phosphate dehydrogenase enzyme in both in vivo and in vitro.

Effect of hyperthermia and lipid peroxidation on the erythrocyte membrane structure

The hyperthermic exposure (39-49 degrees C) of human erythrocyte membranes augmented their lipid peroxidation stimulated by 0.1 mM FeCl3 + 1.5 mM ascorbate while having no significant influence on the non-stimulated lipid peroxidation. No effect of hyperthermia and lipid peroxidation on the post-exposure fluidity of the erythrocyte membrane lipids was found by the fluorescence anisotropy of hexatriene and trimethylaminophenylhexatriene, and excimerization efficiency of pyrene. Exposure to iron/ascorbate increased the accessibility of membrane protein tryptophan residues to acrylamide as judged by fluorescence quenching. These results suggest a higher sensitivity of membrane protein organization than of membrane lipid fluidity to the effect of the system inducing lipid peroxidation.