Polyamine metabolism in MRC-5 cells infected with human cytomegalovirus

The rate of putrescine uptake into MRC-5 cells increased markedly following infection with human cytomegalovirus (HCMV). Enhanced incorporation occurred immediately after infection and the highest levels were attained following the production of infectious, progeny virus. Parallel kinetic changes in the utilization of radio-labelled putrescine were shown by the amounts of spermidine and spermine recovered from infected cells as radioactive derivatives. A temporal correlation was found between these changes in polyamine metabolism and the synthesis of virus DNA. Methylglyoxalbis(guanylhydrazone), an inhibitor of spermidine and spermine synthesis, did not affect virus replication if HCMV-infected cells were exposed to the inhibitor after completion of the eclipse phase of the virus growth cycle. These results show that polyamine metabolism is required only during the initial stages of HCMV replication.