Enhanced Ca2+ uptake by mouse erythrocytes in malarial (Plasmodium berghei) infection

Erythrocytes from Plasmodium berghei-infected mice on incubation either in plasma or artificial isotonic media showed an increase in uptake of 45Ca2+ compared with erythrocytes from uninfected mice. Infected cells (55% parasitaemia) incubated in plasma from normal or infected mice gave uptake rates of 9.8 and 8.1 nmol h-1 per 10(10) cells, assuming equilibrium between added 45Ca2+ and plasma Ca2+. Uptake rates of erythrocytes from infected mice were increased in the presence of glucose, with a rate of 15.0 nmol h-1 per 10(10) cells (52-58% parasitaemia) at 5 mM glucose, compared with 1.5 nmol h-1 per 10(10) cells in the absence of glucose. The enhancement of 45Ca2+ uptake was more pronounced with increasing parasitaemia, and in the fraction relatively enriched with erythrocytes carrying mature parasites. It is likely, therefore, that the enhancement is due to changes in membrane permeability accompanying parasite development. Enhanced haemolysis accompanied 45Ca2+ uptake of erythrocytes carrying mature parasites, but not of those carrying young parasites or uninfected erythrocytes. The possible role of an altered Ca2+ status in erythrocyte pathophysiology during malarial infection is discussed.