Decreased rate of uridine and glycerin uptake in L cells resistant to ethidium bromide

: A comparison was made among rates of uptake of 3H-uridine, 3H-glycerol and 3H-D-xylose into mouse fibroblasts of line L sensitive to ethidium bromide (EB), and into EB-resistant cells obtained from this line by selection. Constants of uridine transport and phosphorylation were determined. For EB sensitive L cells Kt was 162 +/- 27 microM, Vt was 7.5 +/- 0.7 microM/sec. For EB resistant cells Kt was 178 +/- 27 microM, and Vt was 4.6 +/- 0.2 microM/sec. Thus, the transport rate of uridine in resistant cells was twice lower than in EB sensitive cells. The rate of uridine phosphorilation in EB resistant cells was by three times lower than in EB sensitive ones. The uptake of glycerol into resistant cells was also lowered. There was no difference in transport of 3H-D-xylose between sensitive and resistant cells. The data obtained may suggest some changes in plasma membrane in the EB resistant cells.