Plasma and Aqueous Humour Electrolyte Levels, Sodium Pump Activity and Intraoccular Pressure in Glaucoma and Cataract Subjects attending a Nigerian Tertiary Hospital

In this case-controlled study, electrolyte levels in Aqueous Humour (AH) and plasma, sodium/potassium adenosine triphosphatase (Na+/ K+ ATPase) activity as well as intra-occular pressure were measured in normal, cataract and glaucoma participants as possible biomarkers of degenerative diseases of the eye. Three groups of age-matched consenting participants were recruited viz: Non-visually impaired Control, participants with Open-angle glaucoma (cases) and those with cataract (Negative control). AH fluid was surgically collected from glaucoma and cataract participants. Sodium, potassium, chloride and bicarbonate levels were determined in plasma and in the AH fluid using ISE-4000. Red-cell membrane Na+/ K+ ATPase activity and plasma glucose were assayed spectrophotometrically. Blood pressure (BP) and pH were monitored in all participants using standard methods. Data were analysed using ANOVA and significance was at p<0.05. All participants were normotensive and normoglycaemic. Mean Intra-occular Pressure (IOP) was significantly higher in glaucoma. Mean plasma and AH Na+, K+ and Cl- levels in the three groups of participants were similar. Mean AH Cl- (121.70±5.4mmol/L) and HCO3- (13.55 ± 3.71mmol/L) levels in glaucoma were significantly higher when compared with cataract and control groups. Mean Na+/K+ ATPase activity in cases was low (22.35 ±1.09µmiP/µgP/min) in comparison to that of cataract and control [23.40±1.09 and 25±2.0µmiP/µgP/min respectively]. The mean pH of AH in cases was 6.7 in comparison to a pH of 7.2 in all participants plasma. Increased levels of Cl- and HCO3- ions were observed in AH in glaucoma and this may be prognostic for glaucoma subjects.

Keywords
glaucoma; electrolyte levels; Na/K ATPase activity; anion/cation imbalance