The deoxyribonucleoside transport systems of cultured Novikoff rat hepatoma cells

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Abstract
The transport of various deoxyribonucleosides by cultured Novikoff rat hepatoma cells (subline N1S1‐67) follows normal Michaelis‐Menten kinetics. The transport reactions are competitively inhibited by most heterologous deoxy‐ and ribonucleosides and by Persantin and Cytochalasin B. Comparisons of the transport kinetics of the various deoxyribonucleosides (Km and Vmax ) and of the Km/Ki ratios for the inhibitions indicate that deoxythymidine, deoxyuridine and 5‐fluordeoxyuridine are transported by a single system, whereas deoxycytidine and the purine deoxyribonucleosides are transported by other systems. The data suggest that deoxyadenosine, deoxyguanosine and deoxyinosine, are not transported by a single system, but the number of transport systems involved could not be established unequivocally. Similar comparisons also suggest that the deoxyribonucleosides are transported by different systems than the ribonucleosides. All deoxyribonucleoside transport systems are inhibited to about the same extent by Persantin (Ki = 1–2 μM) and Cytochalasin B (Ki = 4–12 μM). The inhibitions of deoxynucleoside transport resulted in corresponding apparent competitive inhibitions of their incorporation into nucleic acids.

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