In vitro effect of methotrexate on erythrocytes rheological variables.

Abstract

Methotrexate is one of the drugs that is generally used in cancer and rheumatoid arthritis treatments. Anemia is one of the adverse reactions found; for which we decided to study the direct effect of methotrexate on erythrocyte rheology in vitro, using normal blood donor samples that were divided in 5 aliquots: one was control and the other were treated , with methotrexat in increasing concentrations. (n: 5, each group). Cell morphology was estimated by light microscope; Rigidity index by filtration; Osmotic fragility (measured photometrically at 540 nm), obtaining X50 value (NaCl mM concentration yielding 50% hemolysis) and β (degree of homogeneity of the cell population). Erythrocyte aggregation was measured by optical densitometry showing S, mean size of red cells aggregates and V, initial velocity of process. There was no alteration of erythrocyte aggregation neither in S nor in V. Presence of methotrexat in incubation medium increased the osmotic fragility (higher X₅₀) as well as heterogeneity of the population response to hyposmolarity in the 1 and 5 µM doses. The former effects added to stomatocytosis and erythrocyte deformability could be related with the anemia in patients under Methotrexat treatment. In erythrocyte aggregation, although the size and speed of the aggregates do not increase in presence of the drug, it would be expected that when the rigid erythrocytes enters the capillaries could give time to the formation of aggregates that difficult circulation. and promote the destruction of red blood cells.