TABLE 3

K_i values for inhibition of uridine transport into TLCT1 and ARAC/D2 stable transfectants by analogs of adenine and adenosine

IC₅₀ values were determined from concentration-effect relationships of Figs. 4 and 5 or from similar experiments (data not shown) as described in Table 1.

	TLCT1 (hCNT1)		ARAC/D2 (hCNT2)
Test Compounds	IC₅₀	K_i	IC₅₀	K_i
	μM		μM
Adenosine	49	39	30	25
2′-Deoxyadenosine	57	44	35	29
5′-Deoxyadenosine	88	68	288	237
2′-3′-Dideoxyadenosine	>500^a	>386	>500^a	>411
l-Adenosine	>250	>193	>300	>246
2-Chloroadenosine	131	101	45	37
8-Chloroadenosine	>300	>232	>300	>246
N⁶-(p-Aminobenzyl)adenosine	36	28	43	35
Caffeine	59	46	125	103
Nicotine	81	63	276	227

↵ a No inhibition observed at 500 μM.