Dose- and time-response studies of sodium o-phenylphenate urinary bladder carcinogenicity in rats.
Dose- and time-response studies of urinary bladder carcinogenesis due to orally administered sodium o-phenylphenate (OPP-Na) were performed using 5-week-old male Fischer 344 rats given diets containing 0 (control), 2500, 5000, 10,000, 15,000 or 20,000 ppm OPP-Na for 104 weeks and fed basal diets until 112 weeks (experiment 1). In addition, rats received diets containing 20,000 ppm OPP-Na for 0 (control), 12, 24, 52 or 104 weeks and were killed at week 112 (experiment 2). In experiment 1, the transitional cell carcinoma (TCC) was the major tumor type in the urinary bladder, and the dose-response curve was steep with many tumors occurring at the high doses of 15,000 and 20,000 ppm. The virtually safe dose at a risk level of 10(-6) for TCCs and papillomas was estimated to be 144 ppm by the Weibull model, a high value similar to that for sodium saccharin. In experiment 2, a few TCCs developed after 24 weeks of treatment, but the time-response curve was also steep with the majority of lesions occurring after longer exposure periods. Based on the observed steepness in dose- and time-responses, any implied cancer risk of OPP-Na at the low doses of interest to man must be considered to be very small.
Niho
N
N
Division of Pathology, National Institute of Health Sciences, Tokyo, Japan.
Shibutani
M
M
Toyoda
K
K
Sato
H
H
Hirose
A
A
Imaida
K
K
Takahashi
M
M
Hayashi
Y
Y
Hirose
M
M
D016573:Agrochemicals / Q000633:toxicity*; D000818:Animals; D001713:Biphenyl Compounds / Q000633:toxicity*; D001835:Body Weight / Q000187:drug effects; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000473:pathology; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D016019:Survival Analysis; D013997:Time Factors; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced* / Q000473:pathology; D014545:Urinary Calculi / Q000473:pathology
D016573:Agrochemicals; D001713:Biphenyl Compounds; D002273:Carcinogens; C004369:2-phenylphenol