Hepatic Kupffer cell phagocytotic function in rats with erythrocytic-stage malaria

In the erythrocytic phase of malaria, Kupffer cells show marked hypertrophy and hyperplasia and are filled with malarial pigment. However, phagocytic function in this state has not been well characterized. The aim of the present study was to use mouse Plasmodium berghei to infect rats with malaria and study the phagocytic function and morphology of Kupffer cells.

We used a recirculating isolated perfused rat liver (IPRL) to quantitate Kupffer cell phagocytic clearance of radiolabeled albumin-latex over 120 min in high parasitemia (53 +/- 6%; n = 7) and low parasitemia (approximately 1%; n = 4) malaria-infected rats and littermate controls (n = 7 and n = 4, respectively). In a further group of high-parasitemic rats, perfusion was ceased after 7 min and liver radioactivity also measured. Electron microscopy was performed after perfusions.

In high-parasitemia malaria rats, clearance of radiolabeled latex from IPRL perfusate over 120 min was significantly (P < 0.01) faster than in controls, with a lower area under the curve (0.19 +/- 0.02 vs 0.43 +/- 0.07 /mL per min, respectively) and shorter half-life (t1/2k; 2.4 +/- 0.6 vs 10.0 +/- 2.3 min, respectively). Low-parasitemia rats were identical to controls. After 7 min perfusion in high-parasitemic rats (n = 4), total radioactivity in liver homogenates was higher than in controls (n = 4; 33.1 +/- 6.2 vs 18.4 +/- 1.9% of injected radiolabel; P < 0.05). Electron microscopy showed latex in Kupffer cells, more abundantly seen in high-parasitemic animals.

Total Kupffer cell phagocytic activity of the liver is markedly increased in rats with a high parasitemic load of malarial P. berghei infection. This is presumed to reflect an upregulation of scavenger activity phagocytosing erythrocytes and their breakdown products.