Resistance of mammalian red blood cells of different size to hypertonic milieu.

This research investigates the resistance of different mammalian red blood cells (RBCs) to hyperosmotic environments, suggesting that RBC size is correlated with the animal’s ability to produce concentrated urine.

Research Scope and Methodology

• The research focused on studying the resistance of mammalian RBCs to hyperosmotic environments, which are areas where the concentration of a solute is higher outside the cells, forcing water to move out through osmosis.
• Six different mammalian species’ RBCs were exposed to ten progressively more hyperosmotic solutions of NaCl, over an extended period of 24 hours, at a low temperature of 5°C. This experimented aimed to view the differences in how RBCs of different sizes respond to such conditions.

Findings and Observations

• The researchers found a direct correlation between the osmolality—the concentration of a solution expressed as the total number of solute particles per kilogram— at which the amount of liberated hemoglobin reached a preset level, in this case, 3-4%, and the volume of the RBC. The relationship was such that cells with a smaller volume had a higher resistance to hyperosmotic conditions as compared to larger cells. This indicates that RBC size affects its resistance to these conditions.
• Similar conclusions have been drawn from existent literature in which maximum urinary tonicities are plotted as a function of RBC volume. Urinary tonicity refers to the concentration of solutes in the urine, with high tonicity indicating a more concentrated urine. The findings suggest that animals capable of producing highly concentrated urine tend to have smaller RBCs.
• The researchers deduced from these observations that RBC volume and maximal urinary tonicity in mammals have a close correlation and might regulate one another. However, it is yet to be proved whether this correlation is due to chance or whether kidney function directly or indirectly affects the size of RBCs.

Implications and Future Research

• The findings from this research represent a significant step in understanding the physiological characteristics of RBCs across various animal species and the factors that might influence these characteristics.
• The identified correlation between RBC size and urinary tonicity could lead to further studies to discover whether this correlation is causal and to understand the mechanisms behind it. This could possibly uncover new insight into how the kidney regulates RBC size.