Nucleic acid precursor synthesis by Plasmodium lophurae parasitizing chicken erythrocytes

Abstract

Chicken erythrocytes parasitized by Plasmodium lophurae were cultured in vitro in the presence of glycine-2- 14C, glycine-U- 14C, and 14C-Na-formate for 10–16 hr. Purines isolated from the acid-soluble fraction (ASF), RNA and DNA of parasitized blood exposed to 14C-glycine contained specific activities equivalent to those of uninfected erythrocyte purines. However, parasitized blood samples incorporated 14C-Na-formate into ASF, RNA and DNA purines to a much greater extent than uninfected blood; the ratio of incorporated formate vs glycine by infected blood samples indicated the absence of a complete de novo purine pathway, but failed to rule out the existence of a partial de novo purine pathway in the host-parasite complex. Adenine-8- 14C and 14C-orotic acid served as purine and pyrimidine nucleotide precursors, respectively, in the P. lophurae-chicken erythrocyte complex; 14C-uracil did not serve as an effective pyrimidine nucleotide precursor under in vitro conditions. Autoradiographic studies failed to demonstrate either the in vivo or in vitro incorporation of 3H-thymidine or 3H-uridine into the nucleic acids of intraerythrocytic stages of P. lophurae.