Metabolism and disposition of [14C]5-amino-o-cresol in female F344 rats and B6C3F1 mice.

The metabolism and disposition of [(14)C]5-amino-o-cresol (AOC) in female F344 rats following oral, intravenous, and dermal administration and in female B6C3F1 mice following oral administration were studied. Greater than 80% of a single oral dose (4.0-357 mg kg(-1)) or intravenous dose (2.7 mg kg(-1)) was excreted in urine within 24 h. When the dosing site was protected from grooming, less than 10% of the dermal dose (2.5 and 26 mg kg(-1), rinsed off after 6 h) was absorbed within 24 h, and most of the absorbed radioactivity was excreted in urine. For the unprotected dermal dose, grooming played a major role in the absorption of AOC. Very little AOC-derived radioactivity was present in the surveyed tissues after 24 or 72 h regardless of route, dose level, or species. Five urinary metabolites were identified: 5-acetamido-1,4-dihydroxy-2-methylbenzene glucuronide, AOC O-glucuronide, AOC O-sulfate, N-acetyl-AOC O-glucuronide, and N-acetyl-AOC O-sulfate.

Determination of the tissue distribution and excretion by accelerator mass spectrometry of the nonadecapeptide 14C-Moli1901 in beagle dogs after intratracheal instillation.

Moli1901 is a 19 residue polycyclic peptide antibiotic which increases chloride transport and water mobilization in airway epithelium. These properties suggest that it may be a useful treatment for cystic fibrosis (CF). In this study, we used accelerator mass spectrometry (AMS) to quantify Moli1901 following administration of only 0.045 microCi of 14C-Moli1901 per dog. Limits of quantitation of AMS were 0.03 (urine) to 0.3 (feces) ng equiv. Moli1901/g. Administration of 14C-Moli1901 by intratracheal instillation (approximately 100 microg) into the left cranial lobe of the lung of beagle dogs resulted in retention of 64% of the dose in the left cranial lobe for up to 28 days. Whole blood and plasma concentrations of 14C were <5 ng/ml at all times after the dose. Concentrations of 14C in whole blood and plasma declined over the first day after the dose and rose thereafter, with the rise in plasma concentrations lagging behind those in whole blood. During the first 3 days after the dose, plasma accounted for the majority of 14C in whole blood, but after that time, plasma accounted for only 25-30% of the 14C in whole blood. Tissue (left and right caudal lung lobe, liver, kidney, spleen, brain) and bile concentrations were low, always less than 0.25% the concentrations found in the left cranial lung lobe. Approximately 13% of the dose was eliminated in urine and feces in 28 days, with fecal elimination accounting for about 10% of the dose. The data presented here are consistent with that obtained in other species. Moli1901 is slowly absorbed and excreted from the lung, and it does not accumulate in other tissues. Moli1901 is currently in the clinic and has proven to be safe in single dose studies in human volunteers and cystic fibrosis patients by the inhalation route. No information on the disposition of the compound in humans is available. This study in dogs demonstrates the feasibility of obtaining that information using 14C-Moli1901 and AMS.

Quantitative analysis of the principle soy isoflavones genistein, daidzein and glycitein, and their primary conjugated metabolites in human plasma and urine using reversed-phase high-performance liquid chromatography with ultraviolet detection.

Soy isoflavones are becoming of increasing interest as nutritional agents which can be used to combat osteoporosis and hyperlipidemia, and are also being considered as potential cancer chemopreventive compounds. However, prior to their formulation and distribution as therapeutic agents, thorough pharmacokinetic and toxicological assessment needs to be completed in men and women in a variety of health conditions in order to ensure their therapeutic efficacy and safety. At this time, studies of purified soy isoflavones are possible, and are being designed to fully evaluate the pharmacological utility of these preparations. In support of these studies, quantitative analysis of soy isoflavones in biological fluids can be accomplished with a wide variety of methods and analytical instrumentation. However, the relatively ubiquitous presence of high-performance liquid chromatography with ultraviolet detection (HPLC-UV) in most analytical laboratories, the relative ease of its operation, and the lesser expense of this instrumentation as compared to more sophisticated techniques such as liquid chromatography-mass spectrometry, offers some distinct advantages for its use in pharmacokinetic studies. In this manuscript, the development and validation of an HPLC-UV method for the quantitation of the principal soy isoflavones, genistein, daidzein, and glycitein, and their primary metabolites, in human plasma and urine is described. This analytical approach allows for pharmacologically relevant concentrations of the analytes and their principle metabolites to be detected, and has been validated in close agreement with the US Food and Drug Administration's guidelines for the validation of methods to be used in support of pharmacokinetic studies.

Disposition of propargyl alcohol in rat and mouse after intravenous, oral, dermal and inhalation exposure.

1. The disposition of propargyl alcohol (PAL) radiolabelled with carbon-14 ([2,3-14C]PAL) was determined in the F344 rat and B6C3F1 mouse following intravenous (i.v.), oral, inhalation and dermal exposure. 2. By 72h following an i.v. (1 mg kg(-1) or oral (50 mg kg(-1) dose, 76-90% of the dose was excreted. Major routes of excretion by rat were urine (50-62%), CO2 (19-26%) and faeces (6-14%). Major routes of exerection by mouse were urine (30-40%), CO2 (22-26%) and faeces (10-20%). Less than 6% of the dose remained in tissues at 72 h. Biliary exeretion of radioactity by rat (62% in 4 h) was much greater than elimination in faeces (6% in 72 h), indicating that PAL metabolites underwent extensive enterohepatic recycling. 3. Dermal exposure studies demonstrated that dermal absorption of PAL was minimal due to its inherent volatility. 4. In the inhalation studies (1, 10 or 100 ppm for 6 h), 23-68% of the radioactivity to which animals were exposed was absorbed. The primary route of excretion was urine (23-53%), and significant portion was exhaled as volatile organics (15-30%). 5. PAL was extensively metabolized by both species. One metabolite was identified as 3,3-bis[(2-(acetylamino)-2-carboxyethyl)thio]-1-propanol, which is consistent with Banijamali et al. (1999).

Comparative metabolism and disposition of gemfibrozil in male and female Sprague-Dawley rats and Syrian golden hamsters.

Gemfibrozil, a human pharmaceutical agent, causes hepatomegaly and hepatic peroxisome proliferation in rats, which have been associated with hepatocarcinogenesis. Hamsters are less susceptible than rats to peroxisome proliferation, and no hepatotoxicity has been reported in humans using gemfibrozil. The relationship between hepatic peroxisome proliferation in rodents and human cancer risk is unclear. We investigated the metabolism and excretion of [14C]gemfibrozil in male and female Sprague-Dawley rats and Syrian golden hamsters to better understand species differences in gemfibrozil-induced toxicity. Bile-duct cannulated rats and hamsters excreted 99% and 7 to 20% of a single i.v. gemfibrozil dose in bile, respectively. Cumulative urinary and fecal excretion of gemfibrozil-derived radioactivity after a single oral dose (30 or 2000 mg/kg) were dependent on species and, in rats, on dose. Hamsters excreted 90% of the dose in urine. Rats excreted 55 to 60% of the dose in feces after the low dose and 55 to 70% in urine after the high dose, suggesting possible saturation of biliary excretion. Repeated administration of the low dose to male rats did not alter the routes of excretion compared to a single dose. Major metabolites present in urine and bile were the glucuronide conjugates of gemfibrozil, the 4'-ring hydroxylated metabolite, and the meta-benzoic acid metabolite. The extensive urinary excretion of radioactivity by hamsters and enterohepatic recycling in rats suggests that rats were exposed to a much higher effective dose of gemfibrozil, which may in part explain the previously reported species differences in gemfibrozil-induced toxicity.

Isolation and identification of novel metabolites of gemfibrozil in rat urine.

Gemfibrozil (GEM) is a clofibrate analog used to treat moderate to severe hypertriglyceridemias. In lab animals, GEM causes peroxisome proliferation, an effect that has been associated with hepatocarcinogenesis in rats. In humans, hepatobiliary disorders, but not carcinogenesis, have been associated with GEM therapy. In the present study [14C]GEM was administered orally to rats at a dose of 2000 mg/kg. At various time points, radioactivity in urine was analyzed by liquid scintillation spectrometry, high-pressure liquid chromatography, liquid chromatography/mass spectrometryn, gas chromatography/mass spectroscopy, and nuclear magnetic resonance. Nine metabolites of GEM were identified, some that have not been reported previously. Although the majority of metabolites were glucuronidated, some nonglucuronidated metabolites were identified in urine, including a diol metabolite (both ring methyls hydroxylated), and the product of its further metabolism, the acid-alcohol derivative (ortho ring methyl hydroxylated, meta ring methyl completely oxidized to the acid). Hydroxylation of the aromatic ring also was a common pathway for GEM metabolism, leading to the production of two phenolic metabolites, only one of which was detected in the urine in the nonconjugated or free form. Also of interest was the finding that both acyl and ether glucuronides were produced, including both glucuronide forms of the same metabolite (e. g., 1-O-GlcUA, 5'-COOH-GEM, and 5'-COO-GlcUA-GEM); the positions and functionality of the glucuronide conjugates were identified using base hydrolysis or glucuronidase treatment, in combination with liquid chromatography/MSn and nuclear magnetic resonance.

Vehicle-dependent oral absorption and target tissue dosimetry of chloroform in male rats and female mice.

Chloroform-induced toxicity in rodents depends on oral dose regimen. We evaluated the absorption and tissue dosimetry of chloroform after gavage administration in various vehicles to male Fischer 344 rats and female B6C3F1 mice. Animals received a single dose of chloroform in corn oil, water, or aqueous 2% emulphor at doses (15-180 and 70-477 mg/kg for rats and mice) and dose volumes (2 and 10 ml/kg for rats and mice) used in previously reported toxicity studies. Blood, liver, and kidney chloroform concentration-time courses were determined. Gavage vehicle had minimal effects on chloroform dosimetry in rats. In mice, however, tissue chloroform concentrations were consistently greater for aqueous versus corn oil vehicle. At the low dose volume used for rats (2 ml/kg) gavage vehicle may not play a significant role in chloroform absorption and tissue dosimetry, at the higher dose volume used for mice (10 ml/kg), vehicle may be a critical factor.