The activities of the membrane-bound ATPases (Na+, K+ -ATPase: E. C. 220.127.116.11; Ca2+-ATPase: E. C. 18.104.22.168, and Mg2+-ATPase: E. C. 22.214.171.124) 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 Km 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, Ki, 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