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The warming properties of the Taurus radiowave blood warmer were studied. The safety limits were the same as for microwave warming (Haemotherm). Hemolysis was noted in units with a hematocrit over 0.75 or containing less than 300 g of blood. The effects of radiowave, microwave and water bath warming on the erythrocyte ATP and 2,3 DPG concentrations were compared. Statistically highly significant differences were found between all these methods. Warming of blood in a +35 degrees C water bath for 3 min had no effect on these parameters. There was, however, a tendency for ATP and 2,3 DPG levels to decrease after 60 min water bath incubation (+37 and +45 degrees C), but to increase levels following electromagnetic warming depending on the age of the warmed erythrocytes. Thus, electromagnetic radiation appeared to influence the red cell metabolism, which cannot be explained by the effect of temperature alone.

Membrane fluidity was studied by electron-spin-resonance techniques in human En(a-) erythrocytes that lack the major membrane sialoglycoprotein, glycophorin A. By using stearic acid spin labels with a doxyl group in the C-12 or C-15 positions, we demonstrated that the hydrophobic core in these cells was more fluid than in normal cells. Surface-located regions in isolated En(a-) membranes, when probed with stearic acid labelled in the C-5 position, appeared more stable than in normal membranes. In isolated En(a-) membranes, protein motion was decreased when probed with a nitroxide derivative of maleimide. After incubation with anti-(glycophorin A) antibodies protein motion and membrane fluidity were increased in normal membranes. This effect was observed also after spectrin depletion, which by itself increased protein motion but decreased membrane fluidity in the hydrophobic core of the membrane. The results show that membrane proteins influence the fluidity of membrane lipids.

Two Finnish variants of reduced erythrocyte glucose-6-phosphate dehydrogenase (G-6-PD) activity were studied. The G-6-PD Espoo variant is characterized by severe enzyme deficiency which is normally non-haemolytic although primaquine sensitive. The other variant, G-6-PD Helsinki, in which the enzyme activity is moderately reduced, is associated with chronic haemolytic anaemia. The activity of the pentose phosphate pathway was not stimulated by methylene blue in G-6-PD Espoo cells, whereas in normal and G-6-PD Helsinki cells there were increases in shunt activity of 64.5- and 5.3-fold, respectively. As judged by the accumulation of 6-phosphogluconate after incubation with 6-aminonicotinamide, the activity of the pentose phosphate pathway was similar in normal and G-6-PD Helsinki cells, whereas in G-6-PD Espoo cells the metabolic flux through this pathway was decreased. Quantities of sulphydryl groups in intact cells and isolated membranes were similar in normal and G-6-PD deficient cells, as revealed by spin label experiments. In contrast to the situation in normal cells, sulphydryl groups in G-6-PD Espoo cells, and to a lesser extent in G-6-PD Helsinki cells, were sensitive to oxidation by acetylphenylhydrazine. In the G-6-PD Helsinki cells, but not in the G-6-PD Espoo cells, membrane fluidity was increased, as judged from the increased mobility of the stearic acid spin label. Mechanisms are discussed by which G-6-PD deficient cells retain adequate levels of NADPH during resting conditions, and it is suggested that the chronic haemolysis associated with G-6-PD Helsinki could be due to a defect in the lipid region of the cell membrane.