Study on membrane fluidity and erythrocyte aggregation in equine, bovine and human species.

The aim of the present paper is to analyze whether membrane fluidity can be predicted from its lipid composition and to assay the possible relationship between such variable and the aggregating properties of erythrocytes from equine, bovine and human species due to the widely acknowledged differences in their tendency to form aggregates. The main difference between phospholipids from plasma membrane in these species lies in the concentration levels of sphyngomyelin (SM) and phosphatidilcoline (PC); more precisely, in the external hemilayer of the lipid bilayer. Membrane fluidity was estimated by the fluorescence polarization method, while erythrocyte aggregation was assessed by an optical method. According to our results, bovine erythrocytes containing high SM and low PC levels, presented the highest anisotropy value as well as an imperceptible aggregation value. Equine erythrocytes, which contain a considerable PC percentage and scarce SM levels, showed the lowest anisotropy value and the highest values of the aggregation parameters. Human erythrocytes presented intermediate values for both properties. Our hypothesis claims that the phospholipid composition would constitute one of the factors determining erythrocyte membrane fluidity and also taking part in the different aggregation tendency shown by equine, bovine and human species.

Effect of hormone replacement therapy upon haemorheological variables.

It is already admitted that hormone replacement therapy (HRT) decreases the risk of developing cardiovascular disease, although its mechanism is not clear yet. In the present work, the effect of the HRT upon cellular and plasmatic haemorheological factors determining blood flow properties: blood viscosity, plasma viscosity, plasma fibrinogen, rigidity erythrocyte index and erythrocyte aggregation rate was studied. Menopausal women were followed through a whole year of HTR. Results demonstrate that after six months of treatment there is a diminution in relative blood viscosity and erythrocyte rigidity, with constant values along the second semester. Erythrocyte aggregation, plasmatic and blood viscosity diminution observed during the treatment can be explained by the simultaneous plasma fibrinogen decrease. Modified cellular and plasmatic rheology could produce beneficial effects on blood flow, particularly in microcirculation, presenting a possible mechanism by which HTR decreases the risk of cardiovascular disease development during menopause.

Haemorheological variables in a rat model of hypertriglyceridaemic obesity and diabetes.

Obesity is a heterogeneous condition of variable aetiology, generally associated with pathologies such as arterial hypertension, hyperlipidaemia, diabetes and cardiac disease. These conditions, either themselves or because of the various treatments used, may further modify blood rheology in an arbitrary manner. Therefore, analyses of changes in the blood rheology induced by obesity in humans have had differing and controversial results. In our laboratory, a model of hypertriglyceridaemic obesity is provided by an inbred rat strain; the beta genotype from the IIMb/Fm strain, presenting a syndrome of moderate obesity with apparent peripubertal onset, associated with hypertriglyceridaemia and glucose intolerance that turns into diabetes. The alpha genotype, originated from the same IIM/Fm stock, represents the control. The present study describes a comparative analysis of the variables determining the rheological behaviour of the blood in obese and control strains. Our results, agreeing with some other studies performed in humans, confirmed the haemorheological changes associated with obesity, and the fact that these changes became more evident in the presence of pathologies such as diabetes. It appears that triglyceridaemia. cholesterolaemia and hyperglycaemia may influence the rheological behaviour of the cell membrane and this damage may provoke a decrease in erythrocyte deformability and, consequently, hyperviscosity of the blood.