Toxicological Review for 2-Methylnaphthalene (CAS No. 91-57-6 ...

Table 1. Distribution of radioactivity in guinea pigs after oral administration of 2-[ 3 H]methylnaphthalene
Tissue 3 hours 6 hours 24 hours 48 hours
Gallbladder
Kidney
Liver
Blood
Lung
Others (combined)
Internal organs
Blood
Gastrointestinal contents
Urine
Feces
Total recovery
Source: Adapted from Teshima et al., 1983.
20.2
5.6
1.7
0.8
0.7
0.8
µg of 3 H/g wet tissue
7
15.7
7.6
2.7
0.7
0.8
1.1
Percent of total administered dose
1.4
0.6
27.9
23.1
0
53
2.1
0.5
20.2
41.3
0
64.2
0.4
0.3
0.2
0.1
0.1
0.2
0.1
0.1
3.1
78.6
10.8
92.7
Griffin et al. (1982) administered single intraperitoneal injections of 400 mg/kg [ 14 C]-2-
methylnaphthalene to male C57BL/6J mice. Groups of 4 mice were sacrificed at 0.5, 1, 3, 6, 12, or 24
hours after injection for measurement of radioactivity in fat, kidney, liver, and lung. Blood 2-
methylnaphthalene concentrations decreased with a reported elimination half-life of 3 hours, indicative
of rapid distribution to other tissues or elimination from the body. Peak tissue concentrations of 2-
methylnaphthalene equivalents (nmol/mg wet weight) were attained about 1 hour after injection in the
liver, 2 hours after injection in the fat, and 4 hours after injection in the kidney and the lung (Griffin et al.,
1982). Peak concentrations were highest in fat (13 nmol/mg), followed by lower concentrations in liver
(3.5 nmol/mg), kidney (2.9 nmol/mg), and lung (0.7 nmol/mg). The results demonstrate that 2-
methylnaphthalene did not preferentially accumulate in the lung although the lung was the only site of
toxicity. Histological examination found that the single 400 mg/kg dose induced bronchiolar necrosis
(minimal to prominent sloughing of lining cells in the bronchiolar lumen as revealed by light microscopy)
in all exposed mice (Griffin et al., 1982). No lesions were found in the liver or kidney of exposed mice
at any time point. Consistent with the attainment of peak lung tissue concentration at 4 hours after
injection, no lesions were evident until 8 hours after injection. The authors also evaluated distribution by
measurement of irreversible binding of label from [ 14 C]-2-methylnaphthalene to various tissues over a
dose (0, 50, 100, 300, and 500 mg/kg; intraperitoneal injection) and time course (1, 2, 4, 8, 12, and
0.04
0.1
0.1
0.1
0.1
0.1
0.1
0.1
1.0
72.2
11.9
85.2