NTP Study Reports
Abstract for TR-423 - 3,4-Dihydrocoumarin
TR-423
Toxicology and Carcinogenesis Studies of 3,4-Dihydrocoumarin (CAS No.
119-84-6)
in F344/N Rats and B6C3F1 Mice (Gavage Studies)
Chemical Formula: C9H8O2 | - | 3D Structure* |
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*To view structure, download free Chemscape Chime Plug-in |
3,4-Dihydrocoumarin was nominated by the Food and Drug Administration and the National Cancer Institute for study because of its widespread use as a flavoring agent in beverages, gelatins, puddings, candy, and other food items; as a fragrance in perfumes, creams, and cosmetics; and because of interest in the structure-activity relationships of the coumarin derivatives.
Toxicity and carcinogenicity studies were conducted by administering 3,4-dihydrocoumarin (99% pure) in corn oil by gavage to groups of male and female F344/N rats and B6C3F1 mice for 16 days, 13 weeks, and 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and peripheral blood cells of mice.
16-DAY STUDY IN RATS
Groups of five male and five female rats received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 190, 375, 750, 1,500, or 3,000 mg/kg body weight 5 days per week for a total of 12 doses in a 16-day period. All male and female rats given 3,000 mg/kg, and four male rats and five female rats given 1,500 mg/kg died. Body weight gains and final mean body weights of rats receiving 190, 375, or 750 mg/kg were similar to those of the controls. There were no clinical findings of organ-specific toxicity or evidence of impaired blood coagulation.
16-DAY STUDY IN MICE
Groups of five male and five female mice received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 140, 280, 560, 1,125, or 2,250 mg/kg body weight 5 days per week for a total of 12 doses in a 16-day period. All mice given 2,250 mg/kg died. Body weight gains and final mean body weights of mice receiving 140, 280, 560, and 1,125 mg/kg were similar to those of the controls. There were no clinical findings of organ-specific toxicity or evidence of impaired blood coagulation.
13-WEEK STUDY IN RATS
Groups of 10 male and 10 female rats received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 75, 150, 300, 600, or 1,200 mg/kg body weight 5 days per week for 13 weeks. Two male rats and five female rats given 1,200 mg/kg died. The body weight gain and final mean body weight of male rats that received 1,200 mg/kg were significantly lower than those of the controls, but the final mean body weights of other dosed groups of male rats and all dosed groups of female rats were similar to or slightly greater than those of the controls. Platelet counts were significantly lower in males and females receiving 600 and 1,200 mg/kg and in females receiving 300 mg/kg. Hemoglobin and hematocrit values and erythrocyte counts were significantly lower in males that received 300 mg/kg or more. The absolute and relative liver and kidney weights of males and females receiving 600 and 1,200 mg/kg were significantly greater than those of the controls. Hepatocellular hypertrophy was observed in rats given 300, 600, and 1,200 mg/kg. The high dose selected for the 2-year study was 600 mg/kg, which was below the level at which mortality, lower final mean body weights, and treatment-related liver lesions were observed.
13-WEEK STUDY IN MICE
Groups of 10 male and 10 female mice received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 100, 200, 400, 800, or 1,600 mg/kg body weight 5 days per week for 13 weeks. Eight male and five female mice receiving 1,600 mg/kg died. Deaths in other groups were attributed to dosing accidents. Final mean body weights of dosed male and female mice were similar to those of the controls, and there were no treatment-related changes in any hematologic parameters. The absolute and relative liver weights of males and females that received 1,600 mg/kg and the relative kidney weight of males that received 1,600 mg/kg were significantly greater than those of the controls. No treatment-related lesions were noted. The high dose selected for the 2-year study was 600 mg/kg, which was below the level at which mortality, lower final mean body weights, and treatment-related liver lesions were observed.
2-YEAR STUDY IN RATS
Groups of 60 male and 60 female rats received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 150, 300, or 600 mg/kg body weight. After 15 months, up to 10 animals from each group were evaluated.
Survival, Body Weights, and Clinical Findings
Survival rates of
dosed
male rats were lower than that of the controls (O mg/kg, 28/51; 150 mg/kg,
12/50; 300 mg/kg, 8/50; 600 mg/kg, 2/50) but survival rates of dosed female
rats were similar to that of the controls (31/50, 21/51, 26/50, 23/51). The
decreased survival in dosed male rats was attributed to a chemical-related
increase in the severity of nephropathy. The final mean body weight of male
rats receiving 600 mg/kg was lower than that of the controls, but the final
mean body weights of other dosed groups of male rats and all dosed groups
of
female rats were similar to those of the controls. No clinical findings related
to chemical administration were observed.
Hematology and Clinical Chemistry
At the 15-month interim
evaluation,
the hemoglobin concentrations, mean erythrocyte volumes, or mean
erythrocyte
hemoglobin concentrations in the 300 and 600 mg/kg female rats were
slightly,
but significantly, lower than those of the controls. In males, only the
hemoglobin concentration in the 600 mg/kg group was significantly lower.
Serum
levels of alkaline phosphatase, alanine aminotransferase, sorbitol
dehydrogenase, or g-glutamyltransferase
in the 300 and 600
mg/kg male rats were
significantly higher than those in the controls. In females, alkaline
phosphatase and g-glutamyltransferase levels were
significantly
higher in the
600 mg/kg group.
Pathology Findings
The principal lesions associated with the
administration of 3,4-dihydrocoumarin to rats occurred in the kidney and
forestomach. There was a chemical related increase in the severity of
nephropathy in all dosed male rats and in 300 and 600 mg/kg female rats.
There
was a corresponding increased incidence of parathyroid gland hyperplasia,
probably as a result of compromised renal function. In the standard evaluation
of single kidney sections, renal tubule adenomas were observed in one 150
and
two 600 mg/kg males and one each in the control, 150, and 300 mg/kg
females.
Transitional cell carcinomas were also observed in two 600 mg/kg male rats.
However, an extended evaluation of step sections identified significantly
higher incidences of focal hyperplasia and adenoma in the 600 mg/kg males
than
in controls (hyperplasia: 0/50, 5/48, 6/47, 8/50; adenoma: 1/50,1/48, 3/47,
6/50).
The incidence of forestomach ulcers in all groups of dosed male rats was significantly greater than that of the controls (4/47, 14/48, 20/50, 16/46).
STOP-EXPOSURE EVALUATION
A group of 40 male rats received 600 mg/kg 3,4-dihydrocoumarin in corn oil by gavage for 9 months, when 20 of the animals were necropsied and evaluated. The remainder of the male rats received only the corn oil vehicle until they died or until the end of the study. Similarly, a group of 30 male rats received 600 mg/kg 3,4-dihydrocoumarin in corn oil by gavage for 15 months, when 10 of the rats were necropsied and evaluated. The remaining 20 rats received only corn oil until the end of the study. A group of 20 vehicle control male rats was necropsied at 9 months, and another 10 vehicle control male rats were necropsied at 15 months.
The severity of nephropathy in male rats of the stop-exposure groups was significantly greater than that of males examined at the 9- and 15-month interim evaluations. This was expected because nephropathy is a progressive degenerative disease that naturally increases in severity with age.
2-YEAR STUDY IN MICE
Groups of 70 male and 70 female mice received 3,4-dihydrocoumarin in corn oil by gavage at doses of 0, 200, 400, or 800 mg/kg body weight. After 15 months, five to 10 animals from each group were evaluated. Additional groups of 8 to 10 animals were evaluated for clinical pathology after 15 months.
Survival, Body Weights, and Clinical Findings
Survival rates of
dosed male and female mice were similar to those of the controls (males: O
mg/kg, 42/50; 200 mg/kg, 39/51; 400 mg/kg, 34/51; 800 mg/kg, 38/50;
females:
36/51, 39/50, 41/50, 28/52). Final mean body weights of dosed male and
female
mice were similar to those of the controls. No clinical findings were noted
that were related to chemical administration.
Hematology and Clinical Chemistry
There were no differences in
hematology or clinical chemistry parameters that were considered to be
chemical
related.
Pathology Findings
The principal neoplasms associated with the
administration of 3,4-dihydrocoumarin to mice occurred in the liver. There
were
significantly increased incidences of hepatocellular adenomas in all groups of
dosed female mice. Further, the incidences of multiple hepatocellular
adenomas
in dosed female mice were greater than that of the controls (control, 0/51; 200
mg/kg, 6/50; 400 mg/kg, 9/50; 800 mg/kg, 9/52). However, there was no
corresponding increased incidence of hepatocellular carcinoma in dosed
female
mice (3/51, 2/50, 4/50, 6/52), and the incidences of hepatocellular adenoma
or
carcinoma were similar between dosed and control male groups (adenoma:
29/50,
23/51, 36/51, 31/50; carcinoma: 11/50, 11/51, 11/51, 6/50).
The incidence of alveolar/bronchiolar adenoma in the 200 and 400 mg/kg male mice was marginally greater than that of the controls (8/50,15/50,15/51,10/50). However, these neoplasms were not considered chemical related because the increased incidence was slight and there was no corresponding increased incidence in the 800 mg/kg group. The incidence of alveolar/bronchiolar neoplasms in female mice was similar between the dosed and control groups (adenoma: 2/51, 5/50, 1/48, 3/51; carcinoma: 0/51, 1/50, 0/48, 0/51).
In the standard evaluation of single sections of kidney, focal hyperplasia and adenoma or carcinoma of the renal tubule were identified in several dosed male mice, but not in controls [adenoma or carcinoma (combined): 0/50,1/51, 2/51,1/49; hyperplasia: 2/50, 2/51, 5/51, 2/49]. In an extended evaluation of step sections, a few additional males with focal hyperplasia or renal tubule adenomas were identified in the dosed groups. However, the incidences of these lesions in dosed groups of male mice were not significantly greater than those of the controls, and did not increase with dose (hyperplasia: 0/50,1/51, 3/51, 1/49; renal tubule adenoma: 0/50, 0/51, 2/51, 1/49). Therefore, the low number of renal tubule neoplasms in male mice was not considered to be chemical related.
GENETIC TOXICOLOGY
3,4-Dihydrocoumarin did not induce gene mutations in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 with or without exogenous metabolic activation (S9). It induced sister chromatid exchanges but not chromosomal aberrations in cultured Chinese hamster ovary cells, with and without S9. No induction of micronuclei was noted in peripheral blood erythrocyte samples obtained from male and female B6C3F1 mice at the end of the 13-week toxicology study.
CONCLUSIONS
Under the conditions of these 2-year gavage studies, there was some evidence of carcinogenic activity of 3,4-dihydrocoumarin in male F344/N rats based on increased incidences of renal tubule adenomas and focal hyperplasia. The transitional cell carcinomas in two 600 mg/kg males may also have been chemical related. There was no evidence of carcinogenic activity of 3,4-dihydrocoumarin in female F344/N rats receiving 150, 300, or 600 mg/kg. There was no evidence of carcinogenic activity of 3,4-dihydrocoumarin in male B6C3F1 mice receiving 200, 400, or 800 mg/kg. There was some evidence of carcinogenic activity in female B6C3F1 mice based on increased incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined).
3,4-Dihydrocoumarin caused ulcers, hyperplasia, and inflammation of the forestomach, parathyroid gland hyperplasia, and increased severity of nephropathy in male rats.
Synonyms: 1,2-benzodihydropyrone, 2H-1-benzopyran-2-one, 2-chromanone, 3,4-dihydro-2H-1-benzopyran-2-one, dihydrocoumarin, hydrocoumarin, o-hydroycinnamic acid, delta-lactone-hydrocinnamic acid, melilotin, melilotine, melilotol, 2-oxochroman
Report Date: September 1993
Pathology Tables, Survival and Growth Curves from NTP 2-year Studies
Target Organs & Incidences from 2-year Studies
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