Microscopic and thermodynamic evaluation of vesicles shed by erythrocytes at elevated temperatures

TL;DR

This study quantitatively analyzes erythrocyte-derived vesicles at elevated temperatures, revealing temperature-dependent increases in vesicle concentration and size, driven by entropy, with potential diagnostic implications for heat stress and cell stability.

Contribution

It provides a novel microscopic and thermodynamic evaluation of vesicle shedding from erythrocytes under heat stress, highlighting entropy-driven processes and potential diagnostic markers.

Findings

Vesicle concentration increases with temperature.

Most vesicles are smaller than 0.4 μm.

Erythrocyte transformation driven by entropy.

Abstract

Erythrocytes and vesicles shed by erythrocytes from human and rat blood were collected and analyzed after temperature was elevated by physical exercise or by exposure to external heat. The images of erythrocytes and vesicles were analyzed by the light microscopy system with spatial resolution of better than 90 nm. The samples were observed in an aqueous environment and required no freezing, dehydration, staining, shadowing, marking or any other manipulation. Temperature elevation, whether passive or through exercise, resulted in significant concentration increase of structurally transformed erythrocytes (echinocytes) and vesicles in blood. At temperature of 37 oC, mean vesicle concentrations and diameters in human and rat blood were (1.50+-0.35)x10^6 and (1.4+-0.2)x10^6 vesicles/{\mu}L, and 0.365+-0.065 and 0.436+-0.03 {\mu}m, respectively. It was estimated that 80% of all vesicles found in human blood are smaller than 0.4 {\mu}m. Thermodynamic analysis of experimental and literature data showed that erythrocyte transformation, vesicle release and other associated processes are driven by entropy with enthalpy-entropy compensation. It is suggested that physical state of hydrated cell membrane is responsible for the compensation. The increase of vesicle number related to elevated temperatures may be indicative of the heat stress level and serve as diagnostic of erythrocyte stability and human performance.