THE OSMOTIC FRAGILITY PATTERN OF HBA, HBAS AND HBSS

1.1     BACKGROUND OF THE STUDY

Globally, haemoglobin (Hb)S is the most common haemoglobin variants and is found most frequently in equatorial Africa and Middle East. (Makani, 2007), approximately 4.5% of the world population carry abnormal Hb (Angastiniotis, 2008), from whom most were detected in parts of Africa; particularly HbS. Sickle cell anemia (SCA) is associated with high morbidity and mortality among sickle cell suffers in developing countries, many children are born with SCA and approximately 5% of these children are believed to die before they reach five years of age.

HbS was suggested to be more common in Sudan particularly in people from western Sudan (Mohammed, 2009). In the Western regions HbS is very well documented among the Albagara, an Afro-Arab constellation of tribes with a predominant African descent (Bayoumi, 2010). In a sub group of Albagara, Misseria, studies showed the prevalence of sickle cell disease (SCD) to be 30%, 16% among immigrants from the Blue Nile province (Ahmed, 2012) and 18% among Nilotes in the south of Sudan (Foy, 2011).

When red blood cells are placed in hypotonic solution in which osmolarity is diminished the gain in red blood cell water is both, instant and quantitative. This phenomenon is put into practical use in the red blood cell osmotic fragility test, which determines the release of haemoglobin from red blood cells in hypotonic sodium chloride (NaCl) solution. Therefore, osmotic fragility index is a measure of the resistance of red blood cells to lysis by osmotic stress (Oyewale and Ajibade, 2012). The test is generally useful to ascertain the level of stability and functionality of plasma membrane (Krogmeier et al., 2013), erythrocyte Mean Cell Volume (MCV) and Surface Area-to-Volume Ratio (SAVR) and diagnosis of hereditary spherocytosis (Alderich et al., 2009; Kumar, 2012). Certain xenobiotics such as primaquine and Fava beans extracts are agents that can interfere with the redox status of red blood cells, specifically in those individuals with impaired glucose–6–phosphate dehydrogenase activity (Mayes, 2011; Champe et al., 2015; Ojo et al., 2012). Other compounds may act in such a way that the activity of certain erythrocyte redox enzymes, such as glutathione reductase (Berker et al., 2010; Forchetti et al., 2009), glutathione peroxidase (Mayes, 2003) and glucose–6–phosphate dehydrogenase (Mayes, 2003; Champe et al., 2015; Ojo et al., 2009), that are required for membrane integrity are compromised. This study is to assess the level of resistance of three various heamoglobins to various concentrations of sodium chloride.

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