Studies on the effect of aqueous extracts of Garcinia kola seeds on human erythrocytes adenosine triphosphatases of HbAA, HbAS and HbSS genotypes

Abstract

The activities of the membrane-bound ATPases (Na⁺, K⁺ -ATPase: E. C. 3.6.1.37; Ca²⁺-ATPase: E. C. 3.6.1.38, and Mg²⁺-ATPase: E. C. 3.6.1.3) were determined in erythrocytes obtained from HbAA, HbAS and HbSS genotypes. For Na⁺, K⁺-ATPase and Ca²⁺-ATPase, the activity trend was HbAA > HbAS > HbSS while for Mg²⁺-ATPase, the trend was HbSS > HbAS > HbAA. The aqueous extract of Garcinia kola seed increased the activity of Na⁺, K⁺-ATPase and Ca²⁺-ATPase in the three genotypes with the trend of HbSS > HbAS > HbAA. Phenylalanine, a known anti-sickling agent, showed similar activating effect as the extract. In contrast, both the extract and phenylalanine decreased the activity of Mg²⁺-ATPase from all the genotypes, showing the trend of HbSS > HbAS > HbAA. The three ATPases obeyed Michaelis-Menten kinetics. The apparent K_m for the three different genotypes for ATP were similar for the ATPases with the values of 5.62+0.02, 5.27+0.02 and 4.65+0.03 mM ATP-Na₂ for (Na⁺, K⁺)- ; Ca²⁺-; and Mg²⁺-ATPases, respectively. An activation constant of 0.317 g/ml of extract, for the Ca²⁺-ATPase of HbSS erythrocyte was obtained while the inhibition constant, K_i, of the extract on Mg²⁺-ATPase from HbSS erythrocyte by the extract was 1.23 g/ml of extract. These findings are of significance to the suggested use of the aqueous extract of G. kola seeds in ameliorating sickle cell crisis.


Key Words: adenosine triphosphatases, erythrocytes, genotypes, phenylalanine


Global Jnl Medical Sciences Vol.2(2) 2003: 107-114