Osmotic and diffusive properties of intracellular water in camel erythrocytes: Effect of hemoglobin crowdedness

Abstract

Camel erythrocytes have exceptional osmotic resistance and is believed to be due to augmented water-binding associated with the high hydrophilicity of camel hemoglobin. In practical terms this means that the proportion of osmotically non-removable water in camel erythrocytes is nearly 3-fold greater than that in human erythrocytes (approximately 65 vs approximately 20%). The relationship between water diffusion and the osmotic characteristics of intracellular water is the subject of this report. The amount of osmotically inactive water is 2-fold greater in camel hemoglobin solution in vitro compared to that of human, but water diffusion does not differ in camel and human hemoglobin solutions. However, the evaluation of water diffusion by magnetic resonance measurements in camel erythrocytes revealed approximately 15% lower apparent diffusion coefficient (ADC) compared with human erythrocytes. When human erythrocytes were dehydrated to the level of camel erythrocytes, their osmotic and water diffusion properties were similar. These results show that a lower ADC is associated with a more pronounced increase in osmotically inactive water fraction. It is proposed that increased hemoglobin hydrophilicity allows not only augmented water-binding, but also a closer hemoglobin packaging in vivo, which in turn is associated with slower ADC and increased osmotic resistance.

Individual Osmotic Fragility Distribution: A New Parameter for Determination of the Osmotic Properties of Human Red Blood Cells

“…The critical osmotic pressure ∏ cj for an individual cell, j , and the critical volume V cj corresponding to it are rewritten in the following form [6]: $\begin{array}{c}\underset{c,j}{\overset{\ast }{{\displaystyle false\prod }}}=\frac{{{\displaystyle false\prod }}_{cj}}{{{\displaystyle false\prod }}_{\text{iso}}}=\frac{V_{\text{iso},\text{j}}-b_j}{V_{c,j}-b_j}.\end{array}$ A distribution of the critical volumes associated with the distribution of critical osmotic pressures is expected. The absolute values of osmotically nonresponsible water are about 3.57 and 0.33 g water/g dry mass in the haemoglobin solution and in the erythrocytes, respectively [10]. It was proposed that the extent of osmotically nonresponsive water correlates with water interacting with protein.…”

“…Protein-water interaction is a key factor in the restriction of water diffusion within the cell. Bogner et al demonstrated that about 20% of intracellular water is directly related to intracellular proteins in terms of osmosis in human erythrocytes [10]. …”

Water and the Cell

“…Conversely polymerization or aggregation of globular proteins, like G actin and hemoglobin, or oligomer formation of monomer proteins causes loss of water accessible surface area (Miller et al, 1987a) with loss of osmotically unresponsive water as the globular proteins dock to one another (Fullerton, 2006c;Bogner et al, 2005). In the case of sickle cell hemoglobin massive polymerization results in osmotic pressure change and cell volume decrease presumably due to loss of osmotically unresponsive water from the hydration shell of unpolymerized hemoglobin (Prouty et al, 1985, also see Fullerton et al, 1987, Bogner et al, 2005and Fullerton et al, 2006c. The extent, structure half-life, and physical properties of the clathrate cluster water theory of Chaplin deserves critical evaluation (see Cluster-Quackery, 2004).…”

Untitled

“…In addition, the augmented water-binding associated with the high hydrophilicity of camel haemoglobin, may contribute to this high osmotic resistance. In fact, according to Bogner et al (2005), the proportion of osmotically non-removable water in camel erythrocytes is nearly 3-fold greater than that in human RBC (approximately 65 vs approximately 20%). On the other hand, erythrocytes of camels show a very low water contents (1.1 -1.3 g water/g dry mass) (Yagil et al, 1974;Weiser et al, 1992;Perk, 2000) and a difference in the major intrinsic membrane water-soluble protein ''spectrin'' which appears to be very tightly bound to the membrane by comparison to those of humans and bovine species (Ralston, 1975).…”