DOCTORAL DISSERTATION 

Abstract

The present thesis concerns factors of major importance in filtrometric studies of human erythrocytes, e.g. influence of buffer media, importance of filtration pressure for filtration through micropores and possible effects of damaged and hemolyzed blood cells. The reproducibility of results from haemorheological studies has also been studied. Furthermore the rheological effects on erythrocytes from experimental, functional manipulation have been studied, e.g. by adding of digitalis glycosides and corticosteroids. Finally, the rheological properties of blood, that has been stored in frozen form, have been evaluated.

The first paperof this thesis shows that red cell morphology, flow behaviour and also the reproducibility of measurements are strongly dependent on the composition of the surrounding buffer medium.

Paper 2points out the importance of a carefully chosen filtration pressure to make the experimental settings to come as close to the in vivo capillary circulatory conditions as possible. Influence from variations in MCV is also demonstrated in this paper.

In paper 3the function of the sodium/potassium pump has, by adding of ouabain, been interfered with, thus creating changes of the intracellular ion and charge conditions. This, in turn, influences on blood viscosity. When incubating erythrocytes with calcium ions a more direct effect on erythrocyte deformability is seen.

In paper 4is described the complex effect of corticosteroids on flow properties of red blood cells. Thus it is shown that the over all effect of adding a corticosteroid to a suspension of blood cells seems to be a decreased viscosity, in spite of the fact that a reduced deformability of red blood cells can be seen as a parallel phenomenon.

Finally, paper 5indicates that the damage caused on red blood cells during preservation by glycerol and in frozen form may be of a haemorheological kind. Filtration through micropores seem: to be an adequate method for evaluation of damage caused to cells by freezing and parallels to the in vivo conditions in the spleen can be seen. The St George's Filtrometer, which was used in this study, seems to be able to find damaged cells in as low concentrations as 1/1000.

It is concluded that a buffer solution, with a small amount of albumin added should be used in studies on filterability of red blood cells. It is also concluded that the cells are sensible to the pressure conditions used in the filtration process. A negative pressure around 30 mm H₂0 seems to be suitable in this type of filtration studies. Haemorheological effects of digitalis glycosides and corticosteroids are elucidated and so is the effect of blood preservation through glycerol treatment and freezing on red blood cells.