Disposition of [14C]hydroquinone in Harlan Sprague-Dawley rats and B6C3F1/N mice: species and route comparison

Hvdroquinone: Assessment of genotoxic potential in the in vivo alkaline comet assay

Hydroquinone (HQ) exposure is common as it is a natural component of plant-based foods and is used in some fingernail polishes, hair dyes, and skin lighteners. Industrially it is used as an antioxidant, polymerization inhibitor, and reducing agent. The current study was undertaken to determine whether HQ may cause DNA damage in an in vivo comet assay in F344 rats. DNA strand breaks were assessed in the duodenum as a direct tissue contact site, the testes, and the liver and kidneys, which were tumor sites in bioassays. Rats were exposed to HQ by gavage at 0, 105, 210, or 420 mg/kg/day. At all dose levels, mean % tail intensity and tail moment values for all tissues in animals given HQ were similar to the control. There were no statistically significant increases in tail intensity in any tissue following HQ treatment of male and female rat and data for all animals fell within the available historical control ranges for each tissue. There was no evidence of induction of DNA damage in cells isolated from duodenum, kidney or liver of male and female rats or in the testes of male rats following exposure to HQ at a dose levels up to 420 mg/kg/day, which caused acute renal necrosis.

Disposition and metabolism of 2,2'-dimorpholinodiethyl ether in sprague dawley rats and B6C3F1/N mice after oral, intravenous administration, and dermal application

The specialty amine catalyst 2,2'-dimorpholinodiethyl ether (DMDEE) is a high-production volume chemical used in the production of flexible foam, high-resilient molded foam, and in coatings and adhesives. The disposition and metabolism of [¹⁴C]DMDEE (20 or 200 mg/kg) were determined in male ane female rats and mice after oral and intravenous administration and dermal application. In male and female rats, following a single oral administration, [¹⁴C]DMDEE was well-absorbed and excreted rapidly and extensively via urine (75-93%) and some in feces (∼4-8%). The total radioactivity in tissues at 24 h and 72 h (males only) following oral administration was 8-10% and ∼4%, respectively, suggesting considerable tissue distribution. A moderate amount of the total tissue radioactivity in kidney and liver were unextractable suggesting covalent binding of [¹⁴C]DMDEE-derived products in tissue macromolecules. Absorption following a single dermal application in rats was significant (∼64%) with a similar disposition pattern to oral. The oral and dermal disposition of [¹⁴C]DMDEE in male and female mice was similar to rats. Urinary products of DMDEE identified were oxidative metabolism of the morpholine ring. Coadministration of DMDEE with nitrite in rats didn't produce the rodent carcinogen, N-nitrosomorpholine.

Disposition and metabolism of N-butylbenzenesulfonamide in Sprague Dawley rats and B6C3F1/N mice and in vitro in hepatocytes from rats, mice, and humans

N-Butylbenzenesulfonamide (NBBS) is a plasticizer detected in the environment suggesting potential human exposure. These studies investigated the in vitro hepatic clearance and disposition of [14C]NBBS in rodents following a single gavage (2, 20 or 200 mg/kg) or intravenous (IV) administration (20 mg/kg). NBBS was cleared slower in hepatocytes from humans compared to rodents. [14C]NBBS was well-absorbed in male rats following gavage administration and excreted extensively in urine (70-76 %) and feces (11-15 %) 72 h following administration. Following a 20 mg/kg gavage dose in male rats, 25 % of the dose was excreted in bile by 24 h suggesting that observed fecal excretion was due to biliary excretion. The radioactivity was distributed to tissues with 14 % and 8 % of the administered dose remaining in tissues at 24 and 72 h, respectively. There was no apparent dose-dependent effect in disposition in male rats. Disposition patterns were similar in female rats (urine, 83 %; feces, 14 %) and male (urine, 69 %; feces, 11 %) and female (urine, 72 %; feces, 9 %) mice following gavage administration of 20 mg/kg. The disposition following IV administration was similar to that of gavage. Urinary radiochemical profiles were similar between doses, routes, species, and sexes. Among numerous metabolites identified, oxidative metabolites of NBBS predominated.

Disposition and metabolism of sulfolane in Harlan Sprague Dawley rats and B6C3F1/N mice and in vitro in hepatocytes from rats, mice, and humans

Sulfolane has been found as a ground water contaminant near refining sites. These studies investigated the in vitro hepatic clearance and in vivo disposition of [¹⁴C]sulfolane in rats and mice following a single oral administration (30, 100, or 300 mg/kg) and dermal application (100 mg/kg).[¹⁴C]Sulfolane was well-absorbed in male rats following oral administration and excreted extensively in urine (≥93%). Total radioactivity in tissues at 24 and 48 h was ∼7% and <2%. Disposition pattern was similar in female rats and male and female mice at 100 mg/kg oral dose.Dermally applied [¹⁴C]Sulfolane (covered dose site, 100 mg/kg) was poorly absorbed in male (∼16%) and female (∼19%) rats; absorption increased to 59% when the dose site was uncovered in male rats suggesting ingestion of dose via grooming of the dose site. Dermally applied [¹⁴C]sulfolane (100 mg/kg, covered dose site) was well absorbed in male (∼70%) and female (∼80%) mice.Urinary radiochemical profiles were similar between routes, species, and sexes; the main analytes present in urine were sulfolane and 3-hydroxysulfolane.Sulfolane was not cleared in hepatocytes from rodents or human suggesting sites other than liver might be involved in metabolism of sulfolane in vivo.