ABSTRACT
Explanted cultures of crystalline lenses have been used to investigate mechanisms of xenobiotic-induced cataract formation. However, very few studies have utilized mechanistic information to predict the cataractogenic potential of structurally diverse xenobiotics. The present investigation outlines how visual assessment of lens clarity, biochemical endpoints of toxicity, and mechanisms of lenticular opacity formation can be used to select compounds with a lower probability of causing cataract formation in vivo. The rat lens explant culture system has been used to screen thiazolidinediones against ciglitazone for their direct cataractogenic potential in vitro. The two compounds that were selected as development candidates (englitazone and darglitazone) did not produce cataracts in rats exposed daily for 3 months. The culture system has also been used to illustrate that the lens is capable of metabolizing compounds to reactive intermediates. In this example, the toxicity of S-(1,2-dichlorovinyl)-L-cysteine (DCVC), a model cataractogen, was attenuated by inhibiting lenticular cysteine conjugate beta-lyase metabolism using aminooxyacetic acid. Finally, this model was used retrospectively to investigate the cataractogenic potential of CJ-12,918 and CJ-13,454 in rats. These compounds showed differences in the incidence of cataract formation in vivo based on differences in hepatic metabolism and penetration of parent drug and metabolites into the lens. The rank order of cataractogenic potential in vitro correlated better with in vivo results when an induced S9 microsomal fraction was added to the culture media. However, the model did not correctly predict the cataractogenic potential of ZD2138, a structurally similar compound. These studies illustrate the use of explant culture to assess mechanisms of cataract formation and outline its use and limitations for predicting cataractogenic potential in vivo.
Subject(s)
Cataract/chemically induced , Drug-Related Side Effects and Adverse Reactions/pathology , Lens, Crystalline/pathology , Thiazolidinediones , Toxicity Tests/methods , Adenosine Triphosphate/metabolism , Aminooxyacetic Acid/pharmacology , Animals , Benzopyrans/antagonists & inhibitors , Benzopyrans/chemistry , Benzopyrans/metabolism , Benzopyrans/toxicity , Biotransformation , Cataract/metabolism , Cataract/pathology , Glutathione/metabolism , Lens, Crystalline/drug effects , Lipoxygenase Inhibitors , Male , Organ Culture Techniques , Rats , Rats, Sprague-Dawley , Thiazoles/antagonists & inhibitors , Thiazoles/chemistry , Thiazoles/metabolism , Thiazoles/toxicity , Xenobiotics/antagonists & inhibitors , Xenobiotics/chemistry , Xenobiotics/metabolism , Xenobiotics/toxicityABSTRACT
Tenidap is a new antirheumatic drug currently undergoing clinical evaluation. It inhibits production and activity of cytokines in vivo and causes significant reductions in plasma markers of disease activity in rheumatoid arthritis. After the oral administration of C-14 labeled tenidap, bile, urine and plasma were examined by HPLC and atmospheric pressure tandem mass spectrometry. Label is excreted primarily in bile/feces and the remainder in urine, with good recoveries. Numerous metabolites were identified and the structures of most were confirmed by comparison with authentic synthetic samples. Hydroxylation in several positions on both the oxindole and thienyl rings of tenidap represents the major routes of metabolism; most of these metabolites are subsequently conjugated. The glucuronide of 5'-hydroxytenidap, excreted primarily in bile, is the major metabolite, constituting about one third of the oral dose recovered. Other pathways include dihydroxylation and methoxylation on the thienyl ring. An unusual reduction of hydroxytenidap took place, resulting in the formation of a novel thiolactone analog. Anaerobic incubation with rat cecal contents generated the thiolactone metabolite, suggesting the involvement of gut microflora.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/metabolism , Indoles/metabolism , Animals , Bile/metabolism , Biotransformation , Carbon Radioisotopes , Chromatography, High Pressure Liquid , Hydroxylation , Indoles/blood , Indoles/urine , Male , Mass Spectrometry , Oxindoles , RatsABSTRACT
A specific high-performance liquid chromatographic-atmospheric pressure chemical ionization tandem mass spectrometric assay for the quantitative determination of beta-tigogenin cellobioside in human serum is described. Serum cleanup and acetylation of the analyte were required to achieve the desired lower limit of quantification, 10 ng/ml. The precision of the assay was better than 13% over a serum concentration range of 10-500 ng/ml.
Subject(s)
Chromatography, High Pressure Liquid/methods , Saponins/blood , Humans , Molecular StructureABSTRACT
A specific high-performance liquid chromatographic/atmospheric pressure chemical ionization tandem mass spectrometric assay for the quantitative determination of tenidap and its D3 analog in human serum is described. The assay exhibited a linear dynamic range of 0.1-25 micrograms ml-1. Its precision for the two analytes over the range was 17% or better. The assay validity and its utility to investigate changes in tenidap bioequivalence and pharmacokinetics are presented.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/blood , Indoles/blood , Mass Spectrometry/methods , Humans , OxindolesSubject(s)
Amines/metabolism , Amines/blood , Amines/urine , Gas Chromatography-Mass Spectrometry , HumansABSTRACT
Accurate quantitative analysis for selected polycyclic aromatic hydrocarbons present on urban dust can be obtained by using a simple procedure consisting of sonic-probe extraction with cyclohexane; clean-up with Florisil((R))-XAD-4((R)), and measurement by high-resolution gas chromatography with flame-ionization detection (HRGC/FID). The analysis can be further simplified by eliminating the clean-up step if HRGC/electron-impact mass-spectrometry (MS) is available. Both the FID and MS methods give results consistent with those obtained by standard procedures. The direct HRGC/MS procedure, combined with chemical ionization, can also be applied to the determination of polycyclic organic materials present in solvent-refined coal, shale oil and crude oil.
ABSTRACT
Atrazine, DDE, and dieldrin were extracted and concentrated from various surface, subsurface, and finished waters using the macroreticular resin method. Organic components in the concentrates from these waters were separated by gas chromatography; the amounts of the three pesticides in the waters ranged from 0.5 to 42,000 parts per trillion by weight. Every major watershed in the State of Iowa revealed some degree of pesticide contamination and seasonal variations were consistent with agricultural runoff models. Atrazine concentrations were highest of the three pesticides, a symptom of its widespread use in the corn belt. DDE also appeared in substantial quantities, providing further evidence of the persistence of DDT and its metabolites. Water from several shallow wells and finished water from many water treatment plants were also contaminated. Current treatment processes do not effectively remove these pesticides.
