Malaria parasites (<i>Plasmodium lophurae</i>) Developing Extracellularly <i>in vitro</i>: Incorporation of Labeled Precursors*

Abstract

SYNOPSIS. P. lophurae were removed from their host duck erythrocytes and incubated in vitro in certain modifications of the red cell extract medium previously described. The extent of incorporation, into material precipitable with trichloracetic acid, of 14 C‐labeled precursors supplied after 15–16 hr of incubation, was determined and compared with effects on structure of the parasites. A decreased concentration of erythrocyte extract, which always resulted in increased numbers of degenerate parasites and decreased development to multinucleate forms, also decreased the incorporation of methionine‐methyl‐ 14 C and orotic‐acid‐6‐ 14 C. It did not affect incorporation of proline‐U‐ 14 C or of choline‐1,2‐ 14 C. With a 1/3rd strength red cell extract, omission of coenzyme A, which increased the proportion of degenerate parasites and usually decreased the multinucleate forms, decreased the incorporation of all 4 substrates, in keeping with the inability of the parasites to synthesize CoA. On the other hand, omission of ATP and pyruvate, which had an even greater deleterious effect on structure of the parasites than omission of CoA, had no effect on incorporation of methionine or orotic acid and probably none on that of choline. Incorporation of adenine was reduced in presence of ATP or AMP, suggesting competition at an uptake site. Incorporation of proline, however, was higher with ATP and pyruvate present, in keeping with the better development of the extracellular parasites. The uptake of proline may depend on an ATPase in the outer of the 2 membranes surrounding the parasite.

Keywords

Affiliated Institutions

• Rockefeller University US

Related Publications