Early induction of Na(+)-dependent uridine uptake in the regenerating rat liver

Na(+)-dependent uridine transport into liver plasma membrane vesicles from partially hepatectomized and sham-operated rats was studied. Preparations purified 6 h after 70% hepatectomy exhibited an increased Vmax of uridine uptake (3.7 vs. 1.4 pmol/mg prot/3 s) without any change in Km (6 microM). Incubation of the vesicles in the presence of monensin decreased uridine uptake although the differences between both experimental groups remained identical. It is concluded that uridine transport is induced early after partial hepatectomy by a mechanism which does not involve changes in the transmembrane Na+ gradient. This is the first evidence in favor of modulation of nucleoside transport into liver cells.