1. Haemozoin formation in the midgut of the blood-sucking insect Rhodnius prolixus.
- Author
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Oliveira MF, Silva JR, Dansa-Petretski M, de Souza W, Braga CM, Masuda H, and Oliveira PL
- Subjects
- Animals, Biological Factors analysis, Biological Factors pharmacology, Chloroquine pharmacology, Crystallization, Female, Heme toxicity, Hemeproteins metabolism, Hemolymph metabolism, Hot Temperature, Intestinal Mucosa metabolism, Intestines chemistry, Lipid Peroxidation drug effects, Microscopy, Electron, Pigments, Biological biosynthesis, Pigments, Biological metabolism, Quinine pharmacology, Rhodnius drug effects, Rhodnius physiology, Spectroscopy, Fourier Transform Infrared, Heme metabolism, Hemeproteins biosynthesis, Rhodnius anatomy & histology, Rhodnius metabolism
- Abstract
Malaria parasites digest haemoglobin and detoxify the free haem by its sequestration into an insoluble dark-brown pigment known as haemozoin (Hz). Until recently, this pigment could be found only in Plasmodium parasites. However, we have shown that Hz is also present in the midgut of the blood-sucking insect Rhodnius prolixus [Oliveira et al. (1999) Nature 400, 517-518]. Here we show that Hz synthesis in the midgut of this insect is promoted by a particulate fraction from intestine lumen. Haem aggregation activity is heat-labile and is inhibited in vitro by chloroquine (CLQ). Inhibition of Hz formation in vivo by feeding insects with CLQ leads to increased levels of haem in the haemolymph of the insect, which resulted in increased lipid peroxidation. Taken together, these results indicate that a factor capable of promoting Hz crystallisation is present in R. prolixus midgut and that this activity represents an important physiological defence of this insect against haem toxicity.
- Published
- 2000
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