Table 3

Inhibition of NNN 5′ and 2′ hydroxylation in rat nasal mucosa microsomes by coumarin, ethoxycoumarin, and nitrosamines3-a

InhibitorRate (pmol/mg/min)
5′-Hydroxylation (lactol)2′-Hydroxylation (keto alcohol)
None364  (100)3-b 226  (100)
NDMA343  (94)228  (101)
NNK37.1  (10.2)59.4  (26.2)
NBzMA9.2  (2.5)5.9  (2.6)
Ethoxycoumarin23.0  (6.3)25.8  (11.4)
Coumarin14.7  (4.0)8.6  (3.8)

  • ↵3-a 1 μM NNN was incubated 10 min with 16 μg/ml protein with no inhibitor or the indicated inhibitor at a final concentration of 200 μM. Values are the average of two determinations, which agreed within 10%.

  • ↵3-b Numbers in parentheses are the percent of control activity.