Alterations in nucleotide content of human lung fibroblasts infected with Mycoplasma pneumoniae.

The nucleotide content of normal MRC-5 human lung fibroblasts and fibroblasts infected with Mycoplasma pneumoniae PI 1428 was determined. Nucleotides from control and infected fibroblasts were extracted with 5% trichloracetic acid. After neutralization of the extracts, the nucleotides in the extracts were separated by anion-exchange chromatography. Significant differences were found between the nucleotide content of the control and infected cells. Nucleotide triphosphate levels were twofold higher in the control fibroblasts than in the infected fibroblasts 4 h after the initiation of infection. At the same time, nucleotide diphosphate and monophosphate levels were higher in the infected fibroblasts than in the control fibroblasts. Determination of the energy charge ratio for each set of nucleotides (adenosine, guanosine, cytidine, and uridine) demonstrated a shift of nucleotide content in the infected fibroblasts. Immediately after infection, the energy charge for each set of nucleotides was higher for the control fibroblasts than it was for the infected fibroblasts. This pattern continued throughout the infection period with only minor exceptions. The work presented here indicates a loss of energy charge in fibroblasts infected with M. pneumoniae and may help to explain some of the metabolic changes and cell damage which accompany infection.