Cyclohexanone oxime

Exposure related observations in humans: other data

Administrative data

Endpoint:

exposure-related observations in humans: other data

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well-documented study which meets basic scientific principles

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Type of study / information:

In vitro study with human erythrocytes

Endpoint addressed:

other: haematotoxicity

Principles of method if other than guideline:

In vitro study with human erythrocytes in vitro

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Cyclohexanone oxime

EC Number:

202-874-0

EC Name:

Cyclohexanone oxime

Cas Number:

100-64-1

Molecular formula:

C6H11NO

IUPAC Name:

cyclohexanone oxime

Test material form:

not specified

Details on test material:

- Name of test material (as cited in study report): cyclohexanone oxime
- Analytical purity: > 99.5%

Method

Details on study design:

Haemoglobin oxidation (HbFe3+) was examined in a) haemolysate, b) erythrocytes, c) erythrocytes after co-incubation with rat liver microsomes and d) erythrocytes after co-incubation with rat hepatocytes

Test substance concentrations: a) and c): 0, 1, 2.5, 5 or 7 (a) or 8 (b) mM; b) and d): 0, 1, 2 or 3 mM

3.5 ml haemolysate or whole blood were mixed with 350 µL of test substance dilution in water or Krebs-Henseleit buffer and incubated unter shaking at 37 °C for 1 h. In experiments c) and d) erythrocytes were co-incubated with microsomes or hepatocytes prepared from Norway rats


HbFe3+, thiobarbituric acid reactive substances (TBARS, for examination of lipid peroxidation) and glutathione were measured with standard procedures.


TBARS were only examined in erythrocytes and haemolysate without microsomes or hepatocytes

Exposure assessment:

measured

Results and discussion

Results:

a) Effect in haemolysate: The test substance was the strongest oxidant amongst structurally related compounds (acetaldoxime, methyl ethyl oxime), producing 1.8% HbFe3+ per mM added, hydroxylamine was much more potent than the parent test substance (50% at 7 mM, compared to approx. 14%)

b) Effect in erythrocytes: the magnitude of effect was lower than in haemolysates with an increase of 1.0% HbFe3+ per mM, hydroxylamine was much more potent than the parent test substance (88% at 3 mM, compared to approx. 4%)

c) Effect in erythrocytes after co-incubation with rat liver microsomes: 0.5% increase per mM (hydroxylamine not tested)

d) Effect in erythrocytes after co-incubation with rat hepatocytes: 0.4% increase per mM, hydroxylamine was much more potent than the parent test substance (81% at 3 mM, compared to approx. 3%)

No induction of lipid peroxidation was observed either in haemolysate or human blood. Hydroxylamine induced weak lipid peroxidation

The test substance did not deplete glutathione, but hydroxylamine did.

Glutathione-S-transferase was inhibited in haemolysate by both the test substance and the main metabolite hydroxylamine, and hydroxylamine was again much more potent than the parent test substance (2,38 U per mM, compared to 0,27 U per mM)

Applicant's summary and conclusion

Conclusions:

The results indicate that Hydroxylamine is the reactive metabolite of the test substance with respect to haemotoxic effects in human blood.

Executive summary:

The test substance produced haemoglobin oxidation in human haemolysate and erythrocytes in vitro. The main metabolite hydroxylamine was much more potent thean the parent drug. The test substance did not deplete glutathione, but hydroxylamine was effective. Both the test substance and the main metabolite hydroxylamine inhibited the glutathione-S-transferase, hydroxylamine was much more potent than the parent test substance.