Iodine

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Published literature study, guideline-comparable with limitations: - No metabolic activated trial. - Lower number of metaphases were scored compared to current OECD guideline. - Based on a similar mode action, release of iodine (I2), data from the iodine, iodine tincture and PVP-I is considered interchangeable

Justification for type of information:

Based on a similar mode action, release of iodine (I2), data from the iodine, iodine tincture and PVP-I is considered interchangeable.
Further information is included as attachment to attached background material.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2007

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

GLP compliance:

not specified

Type of assay:

in vitro mammalian chromosome aberration test

Test material

Test material information

Constituent 1

Reference substance name:

Iodine tincture

IUPAC Name:

Iodine tincture

Details on test material:

Iodine tincture is prepared dissolving 6g iodine and 4 g potassium iodide in 100 mL 70% ethanol.
Source: Yoshida Pharmaceutical, Tokyo, Japan.

Method

Species / strain

Species / strain / cell type:

other: Human dental pulp cells (D824 cells)

Metabolic activation:

without

Test concentrations with justification for top dose:

3-h assay: 0.03%, 0.1%, 0.3%
30-h assay: 0.01%, 0.03%, 0.1%

Vehicle / solvent:

No vehicle

Controls

Untreated negative controls:

yes

Negative solvent / vehicle controls:

not specified

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

Remarks:

3h treatment

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium


DURATION
- Exposure duration: In a first assay, cells were treated for 3h with the agent or 4-nitroquinoline 1-oxide (4NQO) as positive control. In a second assay cells were treated with iodine tincture for 30h.
- Expression time (cells in growth medium): In the first assay, cells were incubated for a further 27 h. In the second assay, cells were continously treated with iodine treated for 30 h, as indicated previously.


SPINDLE INHIBITOR (cytogenetic assays): Colcemid 0.02 µg/mL (GIBCO/Invitrogen, Tokyo, Japan), administered three hours before the end of the incubation period in both assays.
STAIN (for cytogenetic assays): Not reported


NUMBER OF REPLICATIONS: No data on replicates.


NUMBER OF METAPHASES EVALUATED: 100 metaphases per dose group (see result table for info on negative and positive controls).


DETERMINATION OF CYTOTOXICITY
- Method: relative cell number (number of cells treated relative to the number of cells in the control cultures x100). Briefly, D824 cells were plated in triplicate and incubated overnight. The cells were treated with iodine tincture at varying concentrations for 3 h. After washing with fresh medium, cells were incubated for further 27 h. The number of cells was counted after harvesting with 0.25% trypsin. For the 30h experiment, cells were treated for the same period of time.


OTHER EXAMINATIONS:
- Determination of polyploidy and endoreplication: Yes, but counted as chromosome aberrations.

Metaphase chromosomes were prepared as described by Tsutsui et al. (Mutat. Res. 373: 113-123, 1997)

Evaluation criteria:

Statistical significance on the incidence of chromosomal aberrations between treated cultures and control.

Statistics:

P value, χ2 test

Results and discussion

Test results

Test results 1

Species / strain:

mammalian cell line, other: D824 cells

Metabolic activation:

without

Genotoxicity:

negative

Remarks:

3 h exposure

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not specified

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Species / strain:

mammalian cell line, other: D824 cells

Metabolic activation:

without

Genotoxicity:

positive

Remarks:

At highest dose only, 30h exposure

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not specified

Untreated negative controls validity:

valid

Positive controls validity:

not examined

Additional information on results:

See tables below

Any other information on results incl. tables

Table 1: Ability of iodine tincture to induce chromosome aberrations in D824 cells treated for 3 h.

Conc. (%)	Relative cell number (%)	Number of metaphases scored (%)	Type of aberrations (%)						Aberrant metaphases (%)	Polyploidy and endoreduplication
			G	B	E	D	O	F
0	100	500	1	0	0	0	0	0	1.0	3.6
0.03	70	100	0	0	0	0	0	0	0	4.0
0.1	68	100	1	0	0	0	0	0	1.0	7.0
0.3	60	100	0	0	0	0	0	0	0	3.0
4NQO(µM)
0.5	59	100	7	11	1	0	0	0	19.0*	5.0
1.0	52	100	9	21	1	0	0	0	25.0*	19.0*

G, gaps; B, breaks; E, exchanges; D, dicentric chromosomes; O, ring chromosomes; F, fragmentations; 4NQO, 4-nitroquinoline 1-oxide.

*Significantly different from control (P<0.01, χ²test)

Table 2: Ability of iodine tincture to induce chromosome aberrations in D824 cells treated for 30 h.

Conc. (%)	Relative cell number (%)	Number of metaphases scored (%)	Type of aberrations (%)						Aberrant metaphases (%)	Polyploidy and endoreduplication
			G	B	E	D	O	F
0	100	300	1	0	0	0	0	0	1.0	3.0
0.01	110	100	1	0	0	0	0	0	1.0	1.0
0.03	64	100	1	0	0	0	0	0	1.0	1.0
0.1	63	100	5	0	0	0	0	0	5.0*	0

G, gaps; B, breaks; E, exchanges; D, dicentric chromosomes; O, ring chromosomes; F, fragmentations; 4NQO, 4-nitroquinoline 1-oxide.

*Significantly different from control (P<0.05, χ²test)

Applicant's summary and conclusion

Conclusions:

The ability of iodine tincture to induce chromosome aberrations in D284 cells was evaluated in a study desgin similar to OECD testing guideline 473. Iodine tincture induced chromosome aberrations (in a statistically significant manner) only at the highest dose after 30 h of treatment without metabolic activation in D284 cells.

Executive summary:

The ability of iodine tincture to induce chromosome aberrations in D284 cells was evaluated in a study desgin similar to OECD testing guideline 473. In a first assay, D284 cells were treated for 3 h with the agent and then incubated for a further 27 h. In the second experiment, D284 cells were treated continously for 30h. In both cases, three hours before harvest, cells were treated with Colcemid and metaphase chromosome were prepared. Iodine tincture induced chromosome aberrations (in a statistically significant manner) only at the highest dose after 30 h of treatment without metabolic activation in D284 cells.