Nucleic Acid Precursor Incorporation by Eimeria nieschulzi (Protozoa: Apicomplexa) and Jejunal Villus Epithelium*

Autoradiography was used to investigate incorporation of tritiated adenine, adenosine, guanosine and thymidine by Eimeria nieschulzi and rat jejunal villus epithelial cells. At 2 1/2 days postinoculation, parasitized and control tissues were incubated for 20 min in oxygenated Tyrode's solution (37 C, pH 7.5) containing 30 μCi/ml of each nucleic acid precursor. Treatment of tissues with ribonuclease revealed that E. nieschulzi incorporated label from ³H]adenine primarily into RNA while that from ³H]adenosine and ³H]guanosine was present mainly in DNA. Label from ³H]thymidine was not utilized by parasites. Host villus epithelial cells incorporated label from ³H]purines primarily into RNA. Labeled cytoplasmic RNA was significantly increased in parasitized cells after incubation in ³H]adenine. Tritiated nuclear RNA and cytoplasmic RNA were significantly decreased in parasitized cells after incubation in ³H]adenosine. Incorporation of label from ³H]guanosine was similar for parasitized and control cells. A small quantity of label from each ³H]precursor was incorporated into DNA of villus epithelial cell nuclei.