Table 1.

Relative total growth (RTG) and background-corrected mutation frequency (MF/106 viable cells) at the thymidine kinase (TK) locus following treatment with different concentrations of BaP and PhIP alone or in selected combinations.

Treatment and concentration (M)	RTGa	TK MFb
BaP		0.1 ± 1.3
10–10	98.7 ± 0.7	0.1 ± 1.5
10–9	95.1 ± 3.8	0.1 ± 1.8
10–8	87.6 ± 5.9	1.3 ± 1.2
10–7	85.6 ± 6.1	30.1 ± 4.3**
2.5 × 10–7	85.6 ± 7.9	44.5 ± 4.7***
7.5 × 10–7	74.1 ± 1.4	46.5 ± 6.9***
10–6	74.2 ± 4.0	54.4 ± 3.6***
2.5 × 10–6	85.9 ± 6.5	61.4 ± 8.5***
7.5 × 10–6	64.4 ± 0.4	76.9 ± 10.5***
10–5	56.4 ± 7.7	0.1 ± 1.3
PhIP
10–9	98.0 ± 3.9	0.7 ± 0.4
10–8	113.2 ± 3.2	0.1 ± 1.3
10–7	112.6 ± 6.8	5.6 ± 2.4
10–6	114.2 ± 5.9	2.1 ± 1.6
10–5	103.9 ± 2.9	5.1 ± 1.5
5 × 10–5	89.2 ± 4.9	7.0 ± 1.6**
7.5 × 10–5	78.6 ± 4.7	8.8 ± 1.2*
10–4	83.0 ± 5.4	7.9 ± 2.4**
BaP + PhIP
10–9 + 10–9	109.8 ± 8.6	2.47 ± 2.13
10–7 + 10–6	95.2 ± 7.8	43.6 ± 11.38***
10–7 + 5 × 10–5	113.2 ± 12.2	0.1 ± 4.72
10–7 + 10–4	89.4 ± 9.4	4.28 ± 2.81
2.5 × 10–7 + 10–6	117.5 ± 8.8	56.81 ± 10.68***
10–6 + 10–6	118.2 ± 1.2	39.71 ± 4.56*
10–6 + 5 × 10–5	60.1 ± 8.2	17.5 ± 4.17*
10–6 + 10–4	113.7 ± 13.3	2.93 ± 3.14
10–5 + 10–6	48.3 ± 3.4	41.1 ± 5.22***
10–5 + 5 × 10–5	100.9 ± 7.4	16.85 ± 5.28*
10–5 + 10–4	81.6 ± 12.5	7.92 ± 2.49
DMSO negative control average range, 4.9–18.6 MF/106 viable cells; EMS positive control average range, 74.6–125.5 MF/106 viable cells. Historical controls: TK: DMSO, 13.3 ± 9.4 MF/106 viable cells ± standard deviation; EMS (positive control), 99.4 ± 40.4 MF/106 viable cells ± standard deviation. aRTG values are percent means ± standard error of the mean (SEM), n = 3–12. bData are presented as background-corrected means ± standard error of the mean (SEM), n = 3–12. Significance compared with the DMSO control calculated using one-way analysis of variance (ANOVA) with Dunnett’s post-test (*p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001).