Dizinc pyrophosphate

Toxicity to reproduction

Administrative data

Endpoint:

two-generation reproductive toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

A two-gnerational reproductive toxicity study of zinc in rats

Author:

Khan AT, Graham TC, Ogden L, Salwa AS, Thompson SJ, Shireen KF, Mahboob M J

Year:

2007

Bibliographic source:

Environmental Sci. Health Part B 42: 403-415

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Zinc chloride

EC Number:

231-592-0

EC Name:

Zinc chloride

Cas Number:

7646-85-7

Molecular formula:

Cl2Zn

IUPAC Name:

zinc dichloride

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Sprague-Dawley Breeding Laboratories, Harlan Sprague-Dawley, Inc., Indianapolis, IN, USA
- Age at study initiation: 30-35 d
- Housing: Polycarbonate cages with stainless-steel wire lids
- Diet: Rodent chow(Lab Diet, Richmond Standard, PMI Feeds, Inc., St. Louis, MO), ad libitum
- Water: Deionized water, ad libitum
- Acclimation period: 2 wk


ENVIRONMENTAL CONDITIONS
- Temperature: 21.1 to 25.5°C
- Humidity: 50-55%
- Air changes: 1/10 min
- Photoperiod : 12 h light/12 h dark cycle

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: 97% ZnCl2 was dissolved in milli-Q water

Details on mating procedure:

- Length of cohabitation: 21 d
- Proof of pregnancy: Conception (day 0 of gestation)was checked daily in the mornings by looking for the presence or absence of copulatory plugs

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

2 generations

Frequency of treatment:

7 days/week

Details on study schedule:

Dosing (7 days/week) started after two weeks of acclimation and was continued for males and females for 77 days prior to cohabitation. Dosing was continued throughout the periods of cohabitation (21 days) for both sexes. Dosing of female rats was continued throughout the gestation (21 days) and lactation (21 days) periods.
The doses for both sexes were adjusted weekly according to changes in body weight.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

7.5 mg/kg bw/day (actual dose received)

Doses / concentrations 2

Dose / conc.:

15 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

30 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

25

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dosage levels were derived from a 14-day dose range finding study. The maximum tolerated dose (MTD) of ZnCl2 was set at 60 mg/kg bw/day in rats. In order to prevent a large effect of zinc-induced toxicity on non-reproductive tissues interfering with the interpretation of pure reproductive toxicity, the high-dose group (group 4) was set at 1/2 of the established MTD (30.00 mg of ZnCl2/kg bw/day). Likewise, the middose group (group 3) was at 1/4 of the established MTD (15.00 mg of ZnCl2/kg bw/day) and the lowest dose group (group 2) was 1/8 of the established MTD (7.50 mg of ZnCl2/kg bw/day).

Positive control:

no

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily


DETAILED CLINICAL OBSERVATIONS: Yes


BODY WEIGHT: Yes


OTHER:
Hematology and clinical chemistry: Prior to necropsy, the P0 males were anesthetized with a combination of intraperitoneal Pentothal and Isoflo via inhalation. While the male rats were still under anesthesia, blood samples for hematology and clinical chemistries were collected in heparinised 3mL syringes via cardiac puncture. Following sample collection and while still under anesthesia, the animals were exsanguinated and necropsied. All plasma samples were analysed for alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALK), amylase (Amyl), blood urea nitrogen (BUN), creatinine (Crea), cholesterol (Chol), sodium (Na), potassium (K), chloride (Cl), calcium (Ca), phosphorus (Phos), albumin (ALB), total protein (TP), total bilirubin (Tbil), and glucose (Glu) using Roche Cobas Mira S Chemistry Analyser (Roche Diagnostic System, Inc., Somerville, NJ).

Oestrous cyclicity (parental animals):

no specified

Sperm parameters (parental animals):

not specified

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: yes
- Maximum of 8 pups/litter (4/sex/litter); excess pups were killed and discarded.


PARAMETERS EXAMINED
The following parameters were examined in [F1 / F2] offspring: Total litter size, number of stillborn pups per sex, sex distribution, pup body weight and the presence of any obvious external congenital anomalies


GROSS EXAMINATION OF DEAD PUPS:
No

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals, as soon as possible after the last litters in each generation were produced
- Maternal animals: All surviving animals, after the last litter of each generation were weaned


HISTOPATHOLOGY / ORGAN WEIGHTS:

Organ weights: During the necropsy, organ weights were recorded for the kidneys, liver, brain, pituitary, adrenals, pancreas, thymus, spleen, testes, epididymides, prostate, and seminal vesicles. P0 male organ weights were also adjusted to body weight for statistical analysis.

Histopathology: Tissue samples collected from organs listed above for histopathologic evaluation were fixed in either Bouins solution (all reproductive tissues) or 10% neutral buffered formalin (all other tissues). After fixation, the tissue samples were trimmed, processed, embedded in paraffin, cut at 6 μm and stained with hematoxylin and eosin.

Postmortem examinations (offspring):

At the end of cohabitation for the parental F1 males and lactation for the F1 females, the animals were anesthesized, sacrificed and their organ weights were recorded like their P0 parents.

Statistics:

- Kruskal-Wallis test followed by the Mann-Whitney U test for pair-wise comparisons to detect the difference between treatment group and control means
- ANOVA for analysing body-weight change, fertility, litter size, pups’ viability, pups’ body weight, postpartum dam weight and organ weight data between different treatment groups
- Dunnett’s and/or Duncan’s multiple comparison procedures

Reproductive indices:

The reproductive parameters were expressed in terms of indices, weights, ratios and efficiencies that considered all stages from conception to weaning. The parameters were:
- Fertility index (%) = (number of females delivering/number of females cohabited) × 100
- Live birth index (%) = (number of live pups at Day 0/number of pups born) × 100
- 4-d survival index (%) = (number of live pups on Day 4/number of pups alive on day 0) × 100
- Body weights of pups = the body weight of pups were recorded on days 0, 4, 7, 14 and 21
- Sex ratio (%) = (the total number of males on the day of weaning)/ (the total number of females on the day of weaning) × 100
- Food efficiency = (body weight gain/amount of diet consumed) × 100

Offspring viability indices:

- 21-d (weaning) survival index (%) = (number of pups alive on Day 21/number of pups alive on Day 4) × 100
- Litter Size = Number of pups/number of pregnant females

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Aggression/hyperactivity throughout the study in both males and females, hair loss behind the ears in males, vaginal discharges in low and high dose females;

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

The males experienced 0, 8, 20, and 12% mortality in control, low, mid, and high dose groups, respectively (see table 1 in the attachment).
The females experienced 12, 24, 28, and 24% mortality in control, low, mid, and high dose groups, respectively (see table 2 in the attachment). Mortality occurred across all dose groups of P0 females including the control due to a failure of the air-handling system (two days prior to scheduled necropsy) for 24 hours.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

All ZnCl2-treated P0 males experienced significant reduction in body weight after the 1st week of dosing and this trend continued up to the end of the experiment. The total weight gain of males was significantly reduced (dose dependent) in the low-, mid- and high-dose groups. In the P0 females, total weight gain and percent reduction in the low- mid- and high-dose groups were not significantly different from the control. See figure 1 and 3 and table 1 and 2 in the attachment for details.
Postpartum dam body weight: The P0 post-partum dam weights in all dose groups were significantly different from their control groups. See table 3 in the attachment for details.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

no effects observed

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

None of the hemogram or leukogram values of both P0 males and females among the ZnCl2-treated groups were different from those of the control groups. However, there was a trend toward decreased values of Packed Cell Volume (PCV).

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

The clinical chemistry findings in males and females of P0 generation did not show any significant difference from those of their controls. However, in mid- and high-dose males of both generations, there seemed to be a trend toward elevated values of amylase (Amyl), alkaline phosphatase (ALK), and glucose (Glu).

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

In males, the most biologically meaningful lesions were found in the reproductive system (prostatic acinar atrophy and inflammation) and the hematopoietic-lymphoreticular system (splenic lymphoid depletion and hemosiderosis and thymic atrophy) of ZnCl2-treated groups. No significant changes in clinical pathology values or organ weights correlated with these lesions. None of the microscopic changes in target organs were of great magnitude. All unscheduled deaths were confined to the ZnCl2-treated groups, the majority of them probably being related to toxicity, but histomorphologic confirmation of this was not noted. The histopathology observed among the ZnCl2-treated females was similar to that seen in the males, except that no lesions were seen in the reproductive system. The correlations and biological interpretations were also very similar.

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

effects observed, treatment-related

Description (incidence and severity):

In F0 rats, ZnCl2 treatment caused a significant reduction on the fertility, litter size, and the viability indices (Days 0 and 4) were significantly reduced at the high-dose group compared to control. See table 4 in the attachment for details.

Effect levels (P0)

1

Key result

Dose descriptor:

LOAEL

Remarks:

systemic

Effect level:

7.5 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

2

Key result

Dose descriptor:

NOAEL

Remarks:

reproductive

Effect level:

15 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reproductive performance

Target system / organ toxicity (P0)

Critical effects observed:

not specified

Results: P1 (second parental generation)

General toxicity (P1)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Aggression/hyperactivity throughout the study in both males and females, hair loss behind the ears in males, vaginal discharges in low and high dose females;

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

The males experienced 0, 12, 8, and 4% mortality in control, low, mid, and high dose groups, respectively. See table 1 in the attachment for details.
The females experienced 0, 8, 12, and 20% mortality in control, low, mid, and high dose groups, respectively. See table 2 in the attachment for details.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The P1 males in the mid- and high-dose groups experienced a significant reduction in body weight after the first week of dosing and the low-dose group experienced a similar reduction after the 2nd week of dosing. These trends continued up to the end of the expierment. The total weight gain of P1 males was significantly reduced (dose-dependent) in the low-, mid- and high-dose group. In the P1 females, total weight gain and percent reduction in the low- mid- and high-dose groups were not significantly different from the control. See figure 1 and 3 and table 1 and 2 in the attachment for details.
Postpartum dam body weight: The P1 post-partum dam weights in all dose groups were significantly different from their control groups. See table 3 in the attachment for details.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

no effects observed

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

None of the hemogram or leukogram values of both P1 males and females among the ZnCl2-treated groups were different from those of the control groups. However, there was a trend toward decreased values of Packed Cell Volume (PCV).

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

The clinical chemistry findings in males and females of P1 generation did not show any significant difference from those of their controls. However, in mid- and high-dose males of both generations, there seemed to be a trend toward elevated values of amylase (Amyl), alkaline phosphatase (ALK), and glucose (Glu).

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

In P1 males, the unadjusted weights of the brain, spleen, and prostate in all ZnCl2-treated groups, the liver, adrenal, testis and seminal vesicles in mid-dose and the kidney in high-dose were significantly different from their controls. When the organ weights of P1 males were adjusted for body weight, the brain, spleen, and prostate in all ZnCl2-treated groups, the liver, adrenal and seminal vesicles in mid-dose group, and kidney in high-dose group remained significantly different from their controls. The unadjusted organ weights of P1 females that were different from their controls included the brain and spleen in low- mid- and high-dose groups and the kidneys in the high-dose group. Following the adjustments of P1 female organ weights for body weight, the brain and spleen in all dose groups and kidneys in high dose groups were significantly different from controls. See table 8 and 10 in the attachment for details.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

The result of gross pathology evaluation are not shown in the publication. Gross findings related to ZnCl2-treatment in males were primarily seen in the target organ systems (digestive, hematopoietic-lymphoreticular, and reproductive) already established for zinc. Digestive system lesions in the gastrointestinal tract (GIT) (distention, discoloration/hemorrhage and ulceration) and pancreas (smaller than usual) were mostly seen in rats given the two highest doses. Hematopoietic-lymphoreticular system lesions (small spleens and thymuses) were also scattered among the groups of ZnCl2-treated males. In the reproductive tract of the males, the only gross changes noted were small prostates and small seminal vesicles (one each) in the high-dose group. Gross lesions in ZnCl2-treated females generally paralleled those observed in their male counterparts.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

In males, the most biologically meaningful lesions were found in the reproductive system (prostatic acinar atrophy and inflammation) and the hematopoietic-lymphoreticular system (splenic lymphoid depletion and hemosiderosis and thymic atrophy) of ZnCl2-treated groups. No significant changes in clinical pathology values or organ weights correlated with these lesions. None of the microscopic changes in target organs were of great magnitude. All unscheduled deaths were confined to the ZnCl2-treated groups, the majority of them probably being related to toxicity, but histomorphologic confirmation of this was not noted. The histopathology observed among the ZnCl2-treated females was similar to that seen in the males, except that no lesions were seen in the reproductive system. The correlations and biological interpretations were also very similar.

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Reproductive function / performance (P1)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

effects observed, treatment-related

Description (incidence and severity):

ZnCl2 treatment resulted in significant reduction on fertility, viability (d0) and litter size in the high-dose group compared to control. See table 4 in the attachment.

Effect levels (P1)

1

Key result

Dose descriptor:

LOAEL

Remarks:

systemic

Effect level:

7.5 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

2

Key result

Dose descriptor:

NOAEL

Remarks:

reproductive

Effect level:

15 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reproductive performance

Target system / organ toxicity (P1)

Critical effects observed:

not specified

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality / viability:

mortality observed, treatment-related

Description (incidence and severity):

Viability index was significantly reduced in the high-dose group. For details see table 5 in the attachment.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The body weight of F1 pups at day 21 in the high-dose group was significantly lower compared to their control. For details see table 6 in the attachment.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

no effects observed

Description (incidence and severity):

no significant difference was seen in the weaning index

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

no effects observed

Description (incidence and severity):

no significant difference was seen in the sex ratios index

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Histopathological findings:

not examined

Other effects:

not examined

Developmental neurotoxicity (F1)

Behaviour (functional findings):

not examined

Developmental immunotoxicity (F1)

Developmental immunotoxicity:

not examined

Effect levels (F1)

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

15 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

viability

body weight and weight gain

Target system / organ toxicity (F1)

Key result

Critical effects observed:

no

Results: F2 generation

General toxicity (F2)

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality / viability:

mortality observed, treatment-related

Description (incidence and severity):

Viability index was significnatly reduced in the high-dose group. For details see table 5 in the attachment.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The body weight of F2 pups at day 21 in the high-dose group were significantly lower compared to the control. For details see table 6 in the attachment.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

no effects observed

Description (incidence and severity):

no significant difference was seen in the weaning index

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

no effects observed

Description (incidence and severity):

no significant difference was seen in the sex ratios index

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Histopathological findings:

not examined

Other effects:

not examined

Developmental neurotoxicity (F2)

Behaviour (functional findings):

not examined

Developmental immunotoxicity (F2)

Developmental immunotoxicity:

not examined

Effect levels (F2)

Key result

Dose descriptor:

NOAEL

Generation:

F2

Effect level:

15 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

viability

body weight and weight gain

Target system / organ toxicity (F2)

Key result

Critical effects observed:

no

Overall reproductive toxicity

Key result

Reproductive effects observed:

yes

Lowest effective dose / conc.:

30 mg/kg bw/day (actual dose received)

Treatment related:

yes

Relation to other toxic effects:

reproductive effects as a secondary non-specific consequence of other toxic effects

Dose response relationship:

yes

Relevant for humans:

no

Applicant's summary and conclusion

Conclusions:

Under the test conditions, adminsitration of zinc chloride to adult male and female rats throughout maturation, mating, gestation and early lactation resulted in significant systemic toxicity effects as reduced body weight on adults in all dose levels. Reproductive toxicity effects and effects on pups were only seen at the highest dose group (30 mg/kg bw/day). Therefore, a systemic NOAEL could not be determined and a systemic LOAEL of 7.5 mg/kg bw/day was set. For reproducitive toxicity a NOAEL of 15 mg/kg bw/day is concluded.