Vanadium dioxide

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

Well reported study, however, the relevance of the study is limited because only selected parameters were investigated and animals were dosed for only 4 weeks. The test material was insufficiently described, body weight data were recorded but not reported, haematology, clinical biochemistry, FOB, necropsy, ophthalmological examination, thyroid hormones, organ weights and histopathology were not conducted/evaluated, applied doses were not analytically analysed, results were reported only in figures and raw data were not provided, historical control data were not provided either.

Data source

Reference

Reference Type:

publication

Title:

Effect of vanadium on L-ascorbic acid concentration in rat tissues

Author:

Zaporowska, H.

Year:

1994

Bibliographic source:

Gen. Pharmac. Vol. 25, No. 3, pp. 467-470

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Two month old Wistar rats of both sexes received an aqueous solution of ammonium metavanadate (AMV) at a concentration of 0.01, 0.05, 0.15 and 0.30 mg V/mL (corresponding to 0.2, 1, 3 and 6 mM solution) over 4 weeks. Food and water intake was monitored daily, body weight was recorded weekly. At study termination all animals were sacrificed and liver, kidney, adrenals and spleen were isolated for L-ascorbic acid determination.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Ammonium trioxovanadate

EC Number:

232-261-3

EC Name:

Ammonium trioxovanadate

Cas Number:

7803-55-6

Molecular formula:

H4N.O3V

IUPAC Name:

ammonium trioxovanadate

Details on test material:

- Source: Reachim (Russia)
- Molecular formula: NH4VO3

Test animals

Species:

rat

Strain:

Wistar

Remarks:

albino

Sex:

male/female

Details on test animals or test system and environmental conditions:

- Age at study start: two month
- Diet: standard granulated roden laboratory chow- LSM (CLPP, Motycz, Poland)
- Water: control group received deionized drinking water ad libitum, treatment groups received AMV containing drinking water ad libitum
- Housing: animals were individually housed in stainless steel cages under controlled conventional conditions

ENVIRONMENTAL CONDITIONS
- Temperature: 19-20 °C
- Humidity: 60±10 %
- Photoperiod: natural day-night cycle

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

other:

Remarks:

deionized drinking water

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

4 weeks

Frequency of treatment:

drinking water, ad libitum

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0.01 other: mg/mL

Remarks:

males: 1.18±0.01 mg/kg bw/day
females: 1.50±0.23 mg/kg bw/day
(calculated based on ingested amount of AMV solution)

Doses / concentrations 2

Dose / conc.:

0.05 other: mg/mL

Remarks:

males: 4.93±0.15 mg/kg bw/day
females: 6.65±0.27 mg/kg bw/day
(calculated based on ingested amount of AMV solution)

Doses / concentrations 3

Dose / conc.:

0.15 other: mg/mL

Remarks:

males: 12.99±1.42 mg/kg bw/day
females: 13.38±1.79 mg/kg bw/day
(calculated based on ingested amount of AMV solution)

Doses / concentrations 4

Dose / conc.:

0.3 other: mg/mL

Remarks:

males: 22.06±1.29 mg/kg bw/day
females: 26.62±1.41 mg/kg bw/day
(calculated based on ingested amount of AMV solution)

No. of animals per sex per dose:

males:
group 1: 20, group 2: 15, group 3: 16, group 4: 11, group 5: 15
females:
group 1: 20, group 2: 15, group 3: 16, group 4: 13, group 5: 15

Control animals:

yes

Details on study design:

- Rationale for animal assignment: animals were randomly divided into 5 groups

Positive control:

no data

Examinations

Observations and examinations performed and frequency:

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION:
- Food consumption for each animal determined:Yes
- Time schedule for examinations: daily

WATER CONSUMPTION AND COMPOUND INTAKE: Yes
- Time schedule for examinations: daily
The vanadium intake was calculated on the basis of the amount of AMV solution consumed by the rats.

Other examinations:

Determination of L-Ascorbic acid concentration in liver, adrenals, spleen and kidney
All organs were immediately washed with ice-cold phosphate buffered saline (PBS; pH 7.4) and delicate by desiccated with lignin. Then the portions of internal organs were homogenized in ice-cold 0.25 M sucrose. The homogenates (5%; w/v) were centrifuged at 3000 x g 10 min at 4°C. In the obtained supernatant L-ascorbic acid concentration was measured according to the method of Kyaw (1978). All assays were duplicated.

Statistics:

Student's t-test was used for statistical analysis. A value of P < 0.05 was used as the level significance. All results are presented as mean values_ SEM.

Results and discussion

Results of examinations

Clinical signs:

not examined

Mortality:

not examined

Body weight and weight changes:

not specified

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

In animals receiving as sole drinking liquid an aqueous AMV solution of 0.15 and 0.30 mg V/mL concentration, a statistically significant and dose dependent decrease of food uptake was observed as compared with the control.
For details please refer to the field "attached background material".

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

effects observed, treatment-related

Description (incidence and severity):

In animals receiving as sole drinking liquid an aqueous AMV solution of 0.15 and 0.30 mg V/mL concentration, a statistically significant and dose dependent decrease of AMV solution uptake was observed as compared with the control.
For details please refer to the field "attached background material".

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Details on results:

L-ascorbic acid concentration in tissues:
In animals of both sexes receiving as the only drinking fluid the AMV solutions, a distinct tendency of the L-ascorbic acid level to decrease was noted in the liver, kidneys, spleen and adrenals.
For details please refer to the field "attached background material".

Effect levels

1

Dose descriptor:

NOEL

Effect level:

0.3 other: mg/mL

Based on:

element

Sex:

male/female

Basis for effect level:

other: no adverse effect observed

2

Dose descriptor:

NOEL

Effect level:

22.06 mg/kg bw/day (nominal)

Based on:

element

Sex:

male

Basis for effect level:

other: see remarks

3

Dose descriptor:

NOEL

Effect level:

26.62 mg/kg bw/day (nominal)

Based on:

element

Sex:

female

Basis for effect level:

other: no adverse effect observed

Applicant's summary and conclusion

Conclusions:

As reported in several other studies, effects on palatability of vanadium containing fluids were observed in high dose groups. Significant and dose-dependent decreases were observed in L-ascorbic acid levels in spleen, liver, adrenals and kidneys in males exposed to 0.15 and 0.30 mg V/mL and females exposed to 0.05, 0.15 and 0.3 mg V/mL. However, as the adversity of this effect remains questionable (discussed below) and no systemic toxicity was observed, this effect is not considered to be adverse and thus not taken into account for NOAEL setting. Based on this, 0.30 mg V/mL (equivalent to 22.06 mg V/kg bw/day in males and 26.62 mg V/kg bw/day in females) represents the NOEL.

This study is well reported, however, no guideline was followed and only limited parameters were analysed. Significant and dose-dependent decreases were observed in L-ascorbic acid levels in spleen, liver, adrenals and kidneys in males exposed to 0.15 and 0.30 mg V/mL and females exposed to 0.05, 0.15 and 0.3 mg V/mL. Zaporwoska et al. (1993) reported already one year before that L-ascorbic acid levels were decreased in plasma and erythrocytes in rats exposed to ammonium metavanadate. Thus, exposure to ammonium metavanadate seems to be correlated with decreased L-ascorbic acid values in different tissues and body fluids. However, as no systemic toxicity or any other effect was observed, it remains unclear whether mild to moderate L-ascorbic acid depression in tissues is or results in any adverse effects. In a publication of Chan & Reade (1996) Wistar Shionogi rats, unable to synthesize L-ascorbic acid, were supplemented with different doses of L-ascorbic acid to determine the L-ascorbic acid requirements in Wistar rats. After 26 weeks, all animals survived and showed no clinical signs of scurvy. The average weekly body weight gain was normal. A severe L-ascorbic acid deficiency would include perinasal and peri-and intra-oral haemorrhage, joint or intramuscular haemorrhage, weakened or fractured hind limbs, delayed wound healing and a failure to thrive (Clemetson, 1989). As none of these clinical signs were observed in studies reported by Zaporowska (1993, 1994) or Chan & Reade (1996), it is assumed that this mild to moderate L-ascorbic acid depression observed in this study is not an adverse effect.

Apart from that, it has been demonstrated that the toxicity of vanadium increases with its valency. Thus, compounds containing 5 -valent V, such as ammonium metavanadate, are most poisonous. It is known that 5 -valent V enters cells through anion channels, i.e. phosphate or sulfate channels. In cells, 5 -valent V is reduced to 2 -valent VO by some reducing compounds such as L-ascorbic acid and thiol-containing cysteine. Thus, the reported reduction of L-ascorbic acid in several organs and also in blood (Zaporowska et al. 1993) is most likely the result of an enhanced consumption/reduction activity of this compound. However, in contrast to humans, rodents are able to synthesize L-ascorbic acid. Thus, it can be assumed that this reduction of L-ascorbic acid will induce re-synthesis and reduction of L-ascorbic acid is an adaptive but not an adverse effect. Apart from that, it is also noteworthy that humans are not able to synthesize L-ascorbic acid. Thus, it is assumed that the protective reduction of 5 -valent V to 2 -valent VO is performed by another reducing substance and thus, it remains questionable whether a reduction of L-ascorbic acid in rats is relevant for humans.

References:
Clemetson, I.B. et al. (1975): Synthesis and some major functions of vitamin C in aniamsl. Annals of New York Academy of Science 258, 24 -46

Executive summary:

Two-month old Wistar rats of both sexes received an aqueous solution of ammonium metavanadate (AMV) at a concentration of 0.01, 0.05, 0.15 and 0.30 mg V/mL (corresponding to 0.2, 1, 3 and 6 mM solution) over 4 weeks. Food and water intake were monitored daily, body weight was recorded weekly. At study termination all animals were sacrificed, and liver, kidney, adrenals and spleen were isolated for L-ascorbic acid determination.

According to the author the food and fluid consumption was significantly decreased in males and females exposed to 0.15 and 0.30 mg V/mL drinking water. Additionally, the L-ascorbic acid levels in liver, adrenals, spleen and kidneys were significantly and dose-dependently decreased in males and females dosed with 0.05, 0.15 and 0.30 mg V/mL drinking water.