Chloroquine-induced lipidosis in the rat retina: a functional and morphological study

Corneal opacity, reversible retinal lipidosis and irreversible receptor cell degeneration are known to occur after long-term treatment with chloroquine. Female albino Wistar rats (initial age 6 weeks, weight between 100 and 150 g) were treated orally with chloroquine (40-60 mg/kg body weight) for 4 weeks and with 70-80 mg/kg body weight for the following 4 (group A) and 8 weeks (group B). The animals were submitted to electroretinography ERG, and the retinas were prepared for histological investigation. After treatment with chloroquine for 8 weeks, lipidosis-like inclusions could be seen in the rat retina. A deformation of the receptor cell layer was not observed by light microscopy. The a-wave amplitude decreased to 33% and the b-wave amplitude to 40% of the values before treatment. In contrast to group A, we found receptor cell degeneration and macrophage-like cells in the peripheral and central retina in rats treated for 12 weeks. These changes were probably responsible for a-wave and b-wave reductions of 50 and 79% of values before treatment, respectively. It can be assumed that changes in ERG parameters in the first period are caused by lipidosis. Later extremer deformation is induced by receptor cell degeneration and accompanying lipidosis.