Thymidine Transport in Herpesvirus hominis Type 1 and 2 Infected BHK 21 Cells

Increase of dThd-uptake 4 to I2 h after infection of BHK or primary rabbit kidney cells with Herpesvirus hominis of type I or 2 can be considered as an early function of the virus genome, because the presence of Cyd-Ara does not prevent the increase of uptake. However, increase of uptake can be prevented by addition of actinomycin D and cycloheximide early in the synthetic ycle. Two modes of uptake have been differentiated by kinetic analysis: at low sub-strate concentration dThd is taken up by 'facilitated transport', whereas at high substrate concentration (above 2"5 #M) simple diffusion takes place. The Km of transport of normal BHK or primary rabbit kidney cells (I-4 or 0"5/~M respectively) is not changed after infection. Only the Vmax increases from 8 to 26.6 pmol in BHK cells or from 2. 9 to 9"o pmol in primary rabbit kidney cells. This indicates that 'carrier sites ' with identical affinity for dThd-transport are responsible for the increase of transport after infection. This increase of transport is correlated with the induction of a virus coded thymidine kinase (TK) and not with different ypes of c.p.e, or cellular damage. Transport of BdUrd increases in a similar manner to that of dThd after infection; transport of dCyd or dUrd increases only slightly, whereas the mechanism of dAdo or Urd uptake by infected cells is quite different