Pentapotassium triphosphate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Reference

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

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Rats were fed on a diet containing pentapotassium triphosphate at the normal phosphorus level or at a high phosphorus level for 21 d.
Feces and urine were collected on days 17-20 by use of metabolic cages. After the treatment, the animals were sacrificed, blood was obtained by exsanguination and the kidneys were removed.
One kidney, feces and urine samples were ashed and analyzed for calcium, magnesium and phosphorus. Further urinalysis was also conducted. The other kidney was examined histopathologically and stained with Von Kossa stain to detect renal calcification.

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Clea Japan, Tokyo, Japan
- Age at study initiation: four weeks old
- Weight at study initiation: 102-104 g
- Housing: individually in stainless steel wire-mesh cages, on day 17-20: metabolic cages
- Diet (e.g. ad libitum): based on the AIN-93G diet ad libitum
- Water (e.g. ad libitum): demineralised water ad libitum
- Acclimation period: one week with a diet containing 100 mmol phosphorus /kg diet.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22±1°C
- Humidity (%): 60-65%
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DIET PREPARATION
- Mixing appropriate amounts with (Type of food): standard diet (based on AIN-93G)
- Storage temperature of food: 4°C

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The calcium, magnesium and phosphorus contents were determined from the experimental diets; no methodological details were provided.
The food intake of the rats was measured daily.

Duration of treatment / exposure:

21 days

Frequency of treatment:

The rats were given free access to the assigned diet and demineralized water throughout the experimental period.

Remarks:

Doses / Concentrations:
100 mmol phosphorus/kg diet, equivalent to 720 mg/kg bw/day pentapotassium triphosphate (assuming an average rat weight of 140g)
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
397 mmol phosphorus /kg diet, equivalent to 4183 mg/kg bw/day pentapotassium triphosphate (assuming an average rat weight of 140g)
Basis:
nominal in diet

No. of animals per sex per dose:

6 female rats per group

Control animals:

no

Details on study design:

- Rationale for animal assignment (if not random): similar mean body weight

Positive control:

no positive control

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: before and after treatment period.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
Food intake was expressed as mean ± SD of the 6 animals per group in g food per day.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at exsanguination on day 21
- Animals fasted: No data
- How many animals: all
- Parameters checked in table 1 were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: on days 17-20
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters checked in table 1 were examined.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

HISTOPATHOLOGY: Yes (see table 2)

Other examinations:

The calcium, magnesium, and phosphorus content of the kidney were analysed.

Statistics:

The apparent absorption of minerals was calculated as the intake - faecal excretion, and the rate of apparent absorption as (intake - faecal excretion)/intake x 100. Each data value is expressed as the mean ± SE. Data were analysed by two-way ANOVA to determine the effect of the dietary phosphorus level and the form of the phosphate salt. Tukey's test was used to determine the significance of differences in multiple comparisons among groups, differences being considered significant at P < 0.05. All statistical analyses were performed with the SPSS package program ver. 6.15.

Clinical signs:

not specified

Mortality:

not specified

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

effects observed, treatment-related

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

BODY WEIGHT AND WEIGHT GAIN
The mean body of the rats was significantly reduced in the high-dose group (see table 3).

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
Intake of food was significantly lower in the high-dose group (see table 3).

CLINICAL CHEMISTRY
The dietary treatments had no significant influence on the blood serum urea nitrogen concentration (table 5).

URINALYSIS
The administration of the high-phosphate died led to significant increased urinary creatinine level, albumine level, N-acetyl-beta-D-glucosaminidase (NAG) activity and beta-microglobulin level compared to the normal-phosphorus diet. The increased NAG activity, albumin and beta-microglobulin concentration could be the result of a diminished proximal tubular function of the kidneys.
Phosphorus level was significantly increased and calcium and magnesium levels were significantly decreased by high-phosphate diet (see table 5).

ORGAN WEIGHTS
The high-phosphate diet led to significant increase of kidney dry weight by 15% (see table 4).

HISTOPATHOLOGY: NON-NEOPLASTIC
Severe nephrocalcinosis was found in animals fed the high-phosphate diet but not in the normal-phosphate diet (see table 4).

OTHER FINDINGS
Concentrations of calcium, magnesium and phosphorus were significantly increased in the kidneys of animals fed the high-phosphate diet. For calcium the increase was factor 44 compared to the normal-phosphorus diet animals. The relative amount was increased by factor 1.79 for magnesium and 1.71 for phosphorus (see table 4).

Dose descriptor:

NOAEL

Basis for effect level:

other: No concentration-dependent dosing regimen was used.

Remarks on result:

not determinable

Remarks:

no NOAEL identified

Critical effects observed:

not specified

Table 3: Body weight and intake of food and minerals in rats fed on a diet containing different amounts of phosphate salts.

	Normal-phosphorus diet			High-phosphorus diet
Phosphate amount
K5P3O10 [g/kg diet]		7.523		50.926
K5P3O10 [mmol/kg diet]		99		396
Body weight
Initial [g]	104 ± 1			103 ± 2
Final [g]	173 ± 2			159 ± 3	*
Food intake
Food [g/d]	13.4 ± 0.2			11.5 ± 0.2	*
Calcium [mmol/d]	1.94 ± 0.04			1.52 ± 0.04	*
Magnesium [mmol/d]	0.309 ± 0.007			0.235 ± 0.005	*
Phosphorus [mmol/d]	1.43 ± 0.03			4.63 ± 0.11	*

Each value is the mean ± SE, n=6 per group.

* Values are significantly different (P<0.05).

 

Table 4: Kidney analysis for rats fed on a diet containing different amounts of phosphate salts.

	Normal-phosphorus diet		High-phosphorus diet
Dry weight [g/100g bw]	0.090 ± 0.002		0.104 ± 0.003	*
Calcium [mmol/100g dry weight]	1.10 ± 0.05		48.1 ± 6.3	*
Magnesium [mmol/100g dry weight]	3.71 ± 0.13		6.61 ± 0.64	*
Phosphorus [mmol/100g dry weight]	42.0 ± 1.0		71.9 ± 9.3	*
Severity of nephrocalcinosis
Score 0	6/6		0/6
Score 1	0/6		0/6
Score 2	0/6		2/6
Score 3	0/6		4/6

Each value is the mean ± SE, n=6 per group.

* Values with different letters in the same row are significantly different.

Score for nephrocalcinosis: 0 (not detected) < 1 < 2 < 3 (severe)

 

Table 5: Indicators of kidney function in rats fed on a diet containing different amounts of phosphate salts.

	Normal-phosphorus diet		High-phosphorus diet
In blood
Urea nitrogen in serum [mmol/L]	9.20± 0.26		9.04± 0.39
In urine
Creatinine [µmol/d]	39.9± 3.2		52.9± 1.4	*
Albumin [g/mol creatinine]	2.50± 0.26		7.05± 0.81	*
NAG activity [U/mmol creatinine]	1.89 ± 0.14		3.2 ± 0.10	*
beta-Microglobulin [g/mol creatinine]	0.041 ± 0.006		0.091 ± 0.012	*
Calcium [mol/mol creatinine]	0.742 ± 0.069		0.156 ± 0.003	*
Magnesium [mol/mol creatinine]	2.85 ± 0.25		1.05 ± 0.08	*
Phosphorus [mol/mol creatinine]	2.66 ± 0.17		47.2 ± 1.5	*

Each value is the mean ± SE, n=6 per group.

* Values with different letters in the same row are significantly different.

 

Table 6: Apparent absorption of minerals by rats fed on a diet containing different amounts of phosphate salts.

		Normal-phosphorus diet	High-phosphorus diet
Calcium	[mmol/d]	0.944 ± 0.056	0.726 ± 0.031	*
	[%]	48.4 ± 2.5	47.5 ± 2.1
Magnesium	[mmol/d]	0.196 ± 0.013	0.087 ± 0.005	*
	[%]	63.4 ± 3.5	36.9 ± 2.5	*
Phosphorus	[mmol/d]	0.791 ± 0.037	3.79 ± 0.06	*
	[%]	55.3 ± 2.0	82.0± 0.6	*

Each value is the mean ± SE, n=6 per group.

* Values with different letters in the same row are significantly different.

 

Conclusions:

Daily administration of a diet containing high amounts of pentapotassium triphosphate (4183 mg/kg bw/day) over 21 days to female Wistar rats led to severe nephrocalcinosis as seen by Von Kossa staining of the kidneys. Analysis of the kidneys revealed increased accumulation of magnesium and phosphate (factor 1.8 and 1.7, respectively, compared to normal phosphate diet containing 720 mg/kg bw/day) and of calcium (factor 44), strengthening the previous mentioned findings. The nephrocalcinosis is accompanied by diminished proximal tubular resorptions as seen by increased urinary albumin, beta-microglobulin and NAG activity. Correspondingly to the increased uptake of phosphate, also increased excretion of phosphate was observed whereas the excretion of calcium and magnesium was rather diminished.

Executive summary:

To assess whether the amount of daily administered dietary pentapotassium triphosphate influences nephrocalcinosis, this compound was administered for 21 days to female Wistar. The rats received either a normal-phosphate diet containing 720 mg/kg bw/day or a high-phosphate diet (4183 mg/kg bw/day). Faeces and urine were collected on days 17-20 by use of metabolic cages. After the treatment, the animals were sacrificed, blood was obtained by exsanguination and the kidneys were removed. One kidney, feces and urine samples were ashed and analyzed for calcium, magnesium and phosphorus. Further urinalysis was also conducted. The other kidney was examined histopathologically and stained with Von Kossa stain to detect renal calcification.

After 21 days of treatment marked calcification was detected in the high-dose group whereas the low-dose group showed no signs of renal calcification. Analysis of the kidneys revealed increased accumulation of magnesium and phosphate (factor 1.8 and 1.7, respectively, compared to normal phosphate diet) and of calcium (factor 44), strengthening the previous findings. The nephrocalcinosis is accompanied by diminished proximal tubular resorptions as seen by increased urinary albumin, beta-microglobulin and NAG activity. Correspondingly to the increased uptake of phosphate, also increased excretion of phosphate was observed whereas the excretion of calcium and magnesium was rather diminished.

Taken together, the results reveal a formation of marked nephrocalcinosis after increased oral administration of pentapotassium triphosphate to rats which is accompanied by diminished resorptions in the proximal tubulae.

Data source

Reference

Reference Type:

publication

Title:

Greater effect of dietary potassium tripolyphosphate than of potassium dihydrogenphosphate on the nephrocalcinosis and proximal tubular function in female rats from the intake of a high-phosphorus diet.

Author:

Matsuzaki H, Masuyama R, Uehara M, Nakamura K, Suzuki K

Year:

2001

Bibliographic source:

Biosci Biotechnol Biochem. 65(4):928-34; PMID: 11388474

Materials and methods

Objective of study:

absorption

distribution

excretion

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Rats were fed on a diet containing either potassium dihydrogenphosphate or pentapotassium triphosphate at the normal phosphorus level or at a high phosphorus level for 21 d.
Faeces and urine were collected on days 17-20 by use of metabolic cages. After the treatment, the animals were sacrificed, blood was obtained by exsanguination and the kidneys were removed.
One kidney, faeces and urine samples were ashed and analyzed for calcium, magnesium and phosphorus. Further urinalysis was also conducted. The other kidney was examined histopathologically and stained with Von Kossa stain to detect renal calcification.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Pentapotassium triphosphate

EC Number:

237-574-9

EC Name:

Pentapotassium triphosphate

Cas Number:

13845-36-8

Molecular formula:

H5O10P3.5K

IUPAC Name:

pentapotassium triphosphate

Details on test material:

- Name of test materials (as cited in study report): potassium tripolyphosphate, K5P3O10; potassium dihydrogenphosphate, KH2PO4
- Storage condition of test material: 4°C

Radiolabelling:

no

Test animals

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Clea Japan, Tokyo, Japan
- Age at study initiation: four weeks old
- Weight at study initiation: 102-104 g
- Housing: individually in stainless steel wire-mesh cages, on day 17-20: metabolic cages
- Diet (e.g. ad libitum): based on the AIN-93G diet ad libitum
- Water (e.g. ad libitum): demineralised water ad libitum
- Acclimation period: one week with a diet containing 100 mmol phosphorus /kg diet.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22±1°C
- Humidity (%): 60-65%
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

DIET PREPARATION
- Mixing appropriate amounts with (Type of food): standard diet (based on AIN-93G)
- Storage temperature of food: 4°C

Duration and frequency of treatment / exposure:

21 days, daily exposure

Doses / concentrations

Remarks:

Doses / Concentrations:
- normal-phosphate diet: 100 mmol phosphorus per kg diet, equivalent to 640 mg/kg bw/day potassium dihydrogenphosphate (assuming an average rat weight of 140 g) or equivalent to 720 mg/kg bw/day pentapotassium triphosphate (assuming an average rat weight of 140 g)
- high-phosphate diet: 400 mmol phosphorus per kg diet, equivalent to 4404 mg/kg bw/day potassium dihydrogenphosphate (assuming an average rat weight of 140 g) or equivalent to 4183 mg/kg bw/day pentapotassium triphosphate (assuming an average rat weight of 140 g)

No. of animals per sex per dose / concentration:

6 female rats per dose

Control animals:

no

Details on study design:

- Rationale for animal assignment (if not random): similar mean body weight in the groups

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled (delete / add / specify): urine, faeces, blood, kidneys
- Time and frequency of sampling: days 17-20

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled (delete / add / specify): urine, faeces, kidneys
- Time and frequency of sampling: days 17-21
- From how many animals: mean of all 6 animals per group
- Method type(s) for identification: AAS
- Limits of detection and quantification: not given

Statistics:

The apparent absorption of minerals was calculated as the intake - fecal excretion, and the rate of apparent absorption as (intake - fecal excretion)/intake x 100. Each data value is expressed as the mean ± SE. Data were analyzed by two-way ANOVA to determine the effect of the dietary phosphorus level and the form of the phosphate salt. Tukey's test was used to determine the significance of differences in multiple comparisons among groups, differences being considered significant at P < 0.05. All statistical analyses were performed with the SPSS package program ver. 6.15.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

The absorption of calcium, magnesium and phosphate was calculated by subtraction of fecal excretion values by these orally administered.
- potassium dihydrogenphosphate: In the high-dose group, the oral absorption of phosphate was significantly increased (ca. 5-fold) compared to the normal-phosphate diet whereas the uptake of calcium and magnesium were diminished, though differences for calcium are not statistically significant.
- pentapotassium triphosphate: In the high-dose group, the oral absorption of phosphate was significantly increased (4.5-fold) compared to the normal-phosphate diet whereas the uptake of calcium and magnesium were diminished.
- so both the trends regarding dose effects as well as the total amounts of ion uptake are comparable for the tri- and the orthophosphate, but the total phosphorous uptake is lower at both dose levels for triphosphate as compared to orthophosphate.
The values are depicted in table 6.

Details on distribution in tissues:

Only concentrations in the kidneys are reported.
- potassium dihydrogenphosphate: Concentrations of calcium, magnesium and phosphorus were significantly increased in the animals fed the high-phosphorus diet. For calcium the increase was 14-fold compared to the normal-phosphorus diet animals.
- pentapotassium triphosphate: Concentrations of calcium, magnesium and phosphorus were significantly increased in the animals fed the high-phosphorus diet. For calcium the increase was 44-fold compared to the normal-phosphorus diet animals. The relative amount was increased by factor 1.79 for magnesium and 1.71 for phosphorus.
- comparison between the low dose groups: No significant differences are found between the tri- and the orthophosphate.
- comparison between the two high dose groups: The increase of calcium, magnesium and phosphorus concentrations is much more drastic in the pentapotassium triphosphate group then in the potassium dihydrogenphosphate group.
The values are depicted in table 4.

Details on excretion:

Only urinary levels of phosphorous calcium and magnesium were reported. Fecal levels were not reported.
- potassium dihydrogenphosphate: Urinary phosphorus level was significantly increased and calcium and magnesium levels were significantly decreased by high-phosphate diet - -pentapotassium triphosphate: Urinary phosphorus level was significantly increased and calcium and magnesium levels were significantly decreased by high-phosphate diet
- comparison between the low dose groups: all three ions are excreted at lower levels in the triphosphate group as compared to orthophosphate group, but statistical significance was not reached in any case.
- comparison between the two high dose groups: The decrease of calcium, magnesium and concentrations is more drastic while the increase in phosphorous is less severe in the pentapotassium triphosphate group as compared to the potassium dihydrogenphosphate group.
(see table 5).

Metabolite characterisation studies

Metabolites identified:

not measured

Any other information on results incl. tables

Table 3A: Body weight and intake of food and minerals in rats fed on a diet containing different amounts of pentapotassium triphosphate.

	Normal-phosphorus diet			High-phosphorus diet
Phosphate amount
K5P3O10 [g/kg diet]		7.523		50.926
K5P3O10 [mmol/kg diet]		99		396
Body weight
Initial [g]	104 ± 1			103 ± 2
Final [g]	173 ± 2			159 ± 3	*
Food intake
Food [g/d]	13.4 ± 0.2			11.5 ± 0.2	*
Calcium [mmol/d]	1.94 ± 0.04			1.52 ± 0.04	*
Magnesium [mmol/d]	0.309 ± 0.007			0.235 ± 0.005	*
Phosphorus [mmol/d]	1.43 ± 0.03			4.63 ± 0.11	*

Table 3B: Body weight and intake of food and minerals in rats fed on a diet containing different amounts of potassium dihydrogenphosphate

	Normal-phosphorus diet		High-phosphorus diet
Phosphate amount
KH2PO4 [g/kg diet]	6.848		46.361
KH2PO4 [mmol/kg diet]	100		397
Body weight
Initial [g]	102 ± 2		103 ± 1
Final [g]	173 ± 2		175 ± 1
Food intake
Food [g/d]	13.1 ± 0.2		13.3 ± 0.3
Calcium [mmol/d]	1.88 ± 0.06		1.81 ± 0.03
Magnesium [mmol/d]	0.299 ± 0.008		0.272 ± 0.004	*
Phosphorus [mmol/d]	1.39 ± 0.04		5.42 ± 0.08	*

Each value is the mean ± SE, n=6 per group.

* Values are significantly different (P<0.05).

 

Table 4A: Kidney analysis for rats fed on a diet containing different amounts of pentapotassium triphosphate.

	Normal-phosphorus diet		High-phosphorus diet
Dry weight [g/100g bw]	0.090 ± 0.002		0.104 ± 0.003	*
Calcium [mmol/100g dry weight]	1.10 ± 0.05		48.1 ± 6.3	*
Magnesium [mmol/100g dry weight]	3.71 ± 0.13		6.61 ± 0.64	*
Phosphorus [mmol/100g dry weight]	42.0 ± 1.0		71.9 ± 9.3	*
Severity of nephrocalcinosis
Score 0	6/6		0/6
Score 1	0/6		0/6
Score 2	0/6		2/6
Score 3	0/6		4/6

Table 4B: Kidney analysis for rats fed on a diet containing different amounts of potassium dihydrogenphosphate.

	Normal-phosphorus diet		High-phosphorus diet
Dry weight [g/100g bw]	0.089 ± 0.001		0.099 ± 0.004
Calcium [mmol/100g dry weight]	1.01 ± 0.03		14.1 ± 2.0
Magnesium [mmol/100g dry weight]	3.62 ± 0.06		4.38 ± 0.16
Phosphorus [mmol/100g dry weight]	42.1 ± 1.4		50.4 ± 1.5
Severity of nephrocalcinosis
Score 0	6/6		0/6
Score 1	0/6		3/6
Score 2	0/6		3/6
Score 3	0/6		0/6

Each value is the mean ± SE, n=6 per group.

* Values with different letters in the same row are significantly different.

Score for nephrocalcinosis: 0 (not detected) < 1 < 2 < 3 (severe)

Table 5A: Indicators of kidney function in rats fed on a diet containing different amounts of pentapotassium triphosphate.

	Normal-phosphorus diet		High-phosphorus diet
In blood
Urea nitrogen in serum [mmol/L]	9.20± 0.26		9.04± 0.39
In urine
Creatinine [µmol/d]	39.9± 3.2		52.9± 1.4	*
Albumin [g/mol creatinine]	2.50± 0.26		7.05± 0.81	*
NAG activity [U/mmol creatinine]	1.89 ± 0.14		3.2 ± 0.10	*
beta-Microglobulin [g/mol creatinine]	0.041 ± 0.006		0.091 ± 0.012	*
Calcium [mol/mol creatinine]	0.742 ± 0.069		0.156 ± 0.003	*
Magnesium [mol/mol creatinine]	2.85 ± 0.25		1.05 ± 0.08	*
Phosphorus [mol/mol creatinine]	2.66 ± 0.17		47.2 ± 1.5	*

Table 5B: Indicators of kidney function in rats fed on a diet containing different amounts of potassium dihydrogenphosphate

	Normal-phosphorus diet		High-phosphorus diet
In blood
Urea nitrogen in serum [mmol/L]	9.53 ± 0.21		9.04 ± 0.43
In urine
Creatinine [µmol/d]	39.1 ± 1.4		41.5 ± 2.0
Albumin [g/mol creatinine]	2.60 ± 0.19		4.23 ± 0.87
NAG activity [U/mmol creatinine]	1.98± 0.21		2.51± 0.15
beta-Microglobulin [g/mol creatinine]	0.046± 0.004		0.060± 0.005
Calcium [mol/mol creatinine]	0.862± 0.065		0.251± 0.039	*
Magnesium [mol/mol creatinine]	3.03± 0.12		1.88± 0.10	*
Phosphorus [mol/mol creatinine]	3.03± 0.26		71.3± 3.2	*

Each value is the mean ± SE, n=6 per group.

* Values with different letters in the same row are significantly different.

 

Table 6A: Apparent absorption of minerals by rats fed on a diet containing different amounts of pentapotassium triphosphate.

		Normal-phosphorus diet	High-phosphorus diet
Calcium	[mmol/d]	0.944 ± 0.056	0.726 ± 0.031	*
	[%]	48.4 ± 2.5	47.5 ± 2.1
Magnesium	[mmol/d]	0.196 ± 0.013	0.087 ± 0.005	*
	[%]	63.4 ± 3.5	36.9 ± 2.5	*
Phosphorus	[mmol/d]	0.791 ± 0.037	3.79 ± 0.06	*
	[%]	55.3 ± 2.0	82.0± 0.6	*

Table 6B: Apparent absorption of minerals by rats fed on a diet containing different amounts of potassium dihydrogenphosphate.

		Normal-phosphorus diet	High-phosphorus diet
Calcium	[mmol/d]	0.993 ± 0.038	0.898 ± 0.040
	[%]	52.9 ± 1.7	49.6 ± 2.3
Magnesium	[mmol/d]	0.206 ± 0.006	0.119 ± 0.005	*
	[%]	69.0 ± 1.4	43.9 ± 1.9	*
Phosphorus	[mmol/d]	0.817 ± 0.031	4.55 ± 0.09	*
	[%]	58.9 ± 1.5	83.9 ±0.8	*

Each value is the mean ± SE, n=6 per group.

* Values with different letters in the same row are significantly different.

 

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): bioaccumulation potential cannot be judged based on study results
Administration of a diet with increased levels of phosphorous either as potassium dihydrogenphosphate (4404 mg/kg bw/day) or as pentapotassium triphosphate (4183 mg/kg bw/day) led to increased phosphate absorption compared to a diet containing "normal" levels of either potassium dihydrogenphosphate (640 mg/kg bw/day) or pentapotassium triphosphate (720 mg/kg bw/day). This phosphate was incorporated in the kidney resulting in marked nephrocalcinosis affecting renal function. These effects were significantly more severe in the pentapotassium triphosphate high dose group than in the potassium dihydrogenphosphate. Correspondingly, the amount of phosphate excreted in urine was significantly elevated in these two groups.

Executive summary:

To assess whether the amount of daily administered dietary potassium dihydrogenphosphate or pentapotassium triphosphate influence nephrocalcinosis, these compounds were administered for 21 days to female Wistar. The rats received either a normal-phosphorous diet containing either potassium dihydrogenphosphate (640 mg/kg bw/day) or pentapotassium triphosphate (720 mg/kg bw/day) or a high-phosphorous diet (potassium dihydrogenphosphate 4404 mg/kg bw/day, pentapotassium triphosphate 4183 mg/kg bw/day). Faeces and urine were collected on days 17-20 by use of metabolic cages. After the treatment, the animals were sacrificed, blood was obtained by exsanguination and the kidneys were removed. One kidney, feces and urine samples were ashed and analyzed for calcium, magnesium and phosphorus. Further urinalysis was also conducted. The other kidney was examined histopathologically and stained with Von Kossa stain to detect renal calcification.

Administration of a diet with increased levels of potassium dihydrogenorthophosphate led to increased phosphate absorption and decreased magnesium and calcium absorption compared to a diet containing "normal" levels of potassium dihydrogenorthophosphate. The same is true for pentapotassium triphosphate, but here the effects on the uptake of the three ions is even more pronounced. The surplus phosphate was incorporated in the kidney resulting in marked nephrocalcinosis affecting renal function as shown by both clinical chemical parameters and kidney histophathology. Again the seen effects are more pronounced in the high dose pentapotassium triphosphate group than in the potassium dihydrogenorthophosphate high dose group. In both groups correspondingly, the amount of phosphate excreted in urine was significantly elevated.

No significant difference was seen in any analyzed parameter between the two low dose groups.