A Comparative Analysis of Erythrocyte Osmotic Fragility across Vertebrate Taxa

The osmotic fragility of erythrocytes is a parameter thatreflects the ability of cells to endure variations in the osmoticenvironment. The impairment of this ability is often associatedwith a variety of pathologies, encompassing hemolytic anemias, malignanttumors, and cardiovascular dysfunctions. Osmotic fragility exhibitsvariability across different animal taxa and is closely relatedwith ecosystems. We developed the method for assessing osmotic fragilityusing a laser particle size analyzer, which facilitates real-timekinetic monitoring of cell concentration changes under controlledtemperature conditions. The species examined included Homo sapiens, Rattusnorvegicus domestica, Coturnix japonicadomestica, Rana ridibunda, Carassius carassius, and Lampetra fluviatilis. The methodologywas presented in two variants: (1) manual water additions and (2)automated medium dilution. The key parameters characterizing osmoticfragility included H ₅₀ (theosmolality that lysed half of lysis-susceptible cells), H ₉₀ (90% celllysis), and W (population heterogeneityby the degree of lysis resistance). In terms of H ₅₀ and W, the results obtained via thismethod did not differ significantly from those obtained by spectrophotometryand flow cytometry. No significant differences were also observed betweenthe outcomes of automated and manual variants of the method. Erythrocytesof aquatic and semiaquatic animals exhibited significantly higherresistance to hypotonic lysis. Among all species examined, amphibian(Rana ridibunda) and lamprey(Lampetra fluviatilis) erythrocytesdemonstrated the lowest osmotic fragility. The most pronounced variabilityin the degree of lysis resistance was detected among amphibians,with an almost twofold difference compared to other taxa examined.While mammalian (human and rat) erythrocytes exhibited similar fragilitylevels, they were more variable in their resistance profiles. Avianerythrocytes demonstrated a half-lysis occurrence at higher osmolality levelscompared to mammalian erythrocytes, although in the domestic quail(Coturnix japonica domestica),erythrocytes lysed over a considerably wider osmotic range and containeda subset of cells resistant to hypotonic lysis. These findings indicatethat erythrocytes of lower vertebrates share a lower osmotic fragilitycompared to those of higher vertebrates, a phenomenon most likelyattributable to embryonic characteristics, ecto-/endothermy, andhabitat considerations.