A Comparative Analysis of Erythrocyte Osmotic Fragility across Vertebrate Taxa

Abstract

The osmotic fragility of erythrocytes is a parameter that reflects the ability of cells to endure variations in the osmotic environment. The impairment of this ability is often associated with a variety of pathologies, encompassing hemolytic anemias, malignant tumors, and cardiovascular dysfunctions. Osmotic fragility exhibits variability across different animal taxa and is closely related with ecosystems. We developed the method for assessing osmotic fragility using a laser particle size analyzer, which facilitates real-time kinetic monitoring of cell concentration changes under controlled temperature conditions. The species examined included Homo sapiens, Rattus norvegicus domestica, Coturnix japonica domestica, Rana ridibunda, Carassius carassius, and Lampetra fluviatilis. The methodology was presented in two variants: (1) manual water additions and (2) automated medium dilution. The key parameters characterizing osmotic fragility included H ₅₀ (the osmolality that lysed half of lysis-susceptible cells), H ₉₀ (90% cell lysis), and W (population heterogeneity by the degree of lysis resistance). In terms of H ₅₀ and W, the results obtained via this method did not differ significantly from those obtained by spectrophotometry and flow cytometry. No significant differences were also observed between the outcomes of automated and manual variants of the method. Erythrocytes of aquatic and semiaquatic animals exhibited significantly higher resistance to hypotonic lysis. Among all species examined, amphibian (Rana ridibunda) and lamprey (Lampetra fluviatilis) erythrocytes demonstrated the lowest osmotic fragility. The most pronounced variability in 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 fragility levels, they were more variable in their resistance profiles. Avian erythrocytes demonstrated a half-lysis occurrence at higher osmolality levels compared to mammalian erythrocytes, although in the domestic quail (Coturnix japonica domestica), erythrocytes lysed over a considerably wider osmotic range and contained a subset of cells resistant to hypotonic lysis. These findings indicate that erythrocytes of lower vertebrates share a lower osmotic fragility compared to those of higher vertebrates, a phenomenon most likely attributable to embryonic characteristics, ecto-/endothermy, and habitat considerations.