Species differences in the developmental toxicity of procymidone-Placental transfer of procymidone in pregnant rats, rabbits, and monkeys.

To clarify species differences in the developmental toxicity of procymidone (Sumilex®, a fungicide for agricultural use), placental transfer studies were conducted using 14C-labeled procymidone in pregnant rats, rabbits, and monkeys. These studies demonstrated that maternal-to-fetal transfer of the parent compound and its hydroxylated metabolite, which are both weak anti-androgenic agents, occurred more easily than that of other metabolites, with much higher absolute concentrations achieved in the fetal circulation of rats than of rabbits or monkeys. Notably, in rats, the fetal plasma concentration of the hydroxylated metabolite was higher than that of procymidone, especially after repeated oral administration of procymidone. These results suggest that the hydroxylated metabolite is the most relevant metabolite involved in teratogenic activity in rats.

Lack of human relevance for procymidone's developmental toxicity attributable to species difference in its kinetics and metabolism.

The agricultural fungicide procymidone can cause external genitalia abnormalities in rats but not monkeys or rabbits. To investigate the relevance of developmental findings in rats to humans, we conducted in vitro plasma protein binding studies, in vitro metabolism (biotransformation) studies using liver S9 fractions and hepatocytes, and in vivo metabolism and excretion studies using chimeric mice with humanized hepatocytes. On the basis of these results, we concluded that the metabolic and excretion profiles of procymidone in humans are similar to those in monkeys and rabbits but differ from those in rats. From the findings of this and previous studies, we judge the developmental toxicity potential of procymidone to be very low in humans.

Identification of Metabolism and Excretion Differences of Procymidone between Rats and Humans Using Chimeric Mice: Implications for Differential Developmental Toxicity.

A metabolite of procymidone, hydroxylated-PCM, causes rat-specific developmental toxicity due to higher exposure to it in rats than in rabbits or monkeys. When procymidone was administered to chimeric mice with rat or human hepatocytes, the plasma level of hydroxylated-PCM was higher than that of procymidone in rat chimeric mice, and the metabolic profile of procymidone in intact rats was well reproduced in rat chimeric mice. In human chimeric mice, the plasma level of hydroxylated-PCM was less, resulting in a much lower exposure. The main excretion route of hydroxylated-PCM-glucuronide was bile (the point that hydroxylated-PCM enters the enterohepatic circulation) in rat chimeric mice, and urine in human chimeric mice. These data suggest that humans, in contrast to rats, extensively form the glucuronide and excrete it in urine, as do rabbits and monkeys. Overall, procymidone's potential for causing teratogenicity in humans must be low compared to that in rats.

Metabolism of metofluthrin in rats: I. Identification of metabolites.

1. Metofluthrin (2,3,5,6-tetrafluoro-4-(methoxymethyl)benzyl (Z/E)-(1R)-trans-2,2-dimethyl-3-(1-propenyl)-cyclopropanecarboxylate) is a novel pyrethroid insecticide, which has E/Z isomers at prop-1-enyl group. 2. Rats were orally dosed with each [14C]-labelled E/Z isomer, and the excreta were collected for isolation and identification of metabolites. Analysis of the excreta by LC/MS and NMR revealed formation of 33 and 23 (total 42) metabolites from rats dosed with Z-isomer and E-isomer, respectively. 3. Major metabolic reactions were cleavage of ester linkage, O-demethylation, hydroxylation, epoxidation or reduction of double bond, glutathione conjugation and its further metabolism, hydroxylation of epoxide and formation of lactone ring. Notably, the acid side, 2,2-dimethyl-3-(1-propenyl)-cyclopropanecarboxylic acid, was much more variously metabolised compared to chrysanthemic acid, the acid side of the known pyrethroids. 4. Major metabolites for Z-isomer mostly retained ester linkage with 1,2-dihydroxypropyl group and/or 2-methylalcohol of cyclopropane ring, while most of those for E-isomer received hydrolysis of the ester linkage without oxidation at the 1-propenyl group or the gem-methyl groups, suggesting epoxidation and hydroxylation could occur more easily on Z-isomer. 5. As the novel metabolic pathways for pyrethroids, isomerisation of ω-carboxylic acid moiety, reduction or hydration of double bond and cleavage of cyclopropane ring via epoxidation were suggested.

Metabolism of metofluthrin in rats: II. Excretion, distribution and amount of metabolites.

1. 14 C-Labelled E/Z isomers of a synthetic pyrethroid metofluthrin ((E/Z)-(1 R,3 R)-2,3,5,6-tetrafluoro-4-(methoxymethyl)benzyl 2,2-dimethyl-3-(1-propenyl)-cyclopropanecarboxylate, abbreviated as RTE/RTZ, respectively) were used for rat metabolism studies. 14 C-RTE or RTZ labelled at the carbonyl-carbon [acid-14C] or the methoxymethylbenzyl-α-carbon [alcohol-14 C] was administered orally to rats at 1 and 20 mg/kg. 2. Dosed compounds were mostly absorbed, metabolised, and rapidly excreted. Dose-related increase in blood AUC suggested no saturation of absorption at the high dose. Blood 14 C was maximal at 3-8 h and decreased with a half-life of 52-163 h. Radioactivity in tissues, blood and plasma decreased basically at the same rate and the sum fell below 0.2% of the dose at 168 h. 3. Although the major metabolic pathways of the isomers, that is, ester cleavage, O-demethylation and ω-oxidation, were similar, there was a notable difference. The RTZ double bond commonly undergoes epoxidation while RTE double bond mainly undergoes glutathione conjugation, which causes faster elimination from plasma and greater excretion into faeces on RTE. Faster urinary excretion and elimination from blood were observed for the alcohol moiety than the acid moiety. 4. In conclusion, this study described the overall metabolic profiles of metofluthrin and identified the differences in metabolic breakdown between the isomers. No marked sex-/dose-related differences were observed.

Metabolism of procymidone derivatives in female rats.

PCM-CH2OH [N-(3,5-dichlorophenyl)-1-hydroxymethyl-2-methylcyclopropane-1,2-dicarboximide] and PA-CH2OH [2-carboxyl-N-(3,5-dichlorophenyl)-1-hydroxymethyl-2-methylcyclopropane-1-carboxamide] are metabolites of the fungicide procymidone [N-(3,5-dichlorophenyl)-1,2-dimethylcyclopropane-1,2-dicarboximide] in rat. The distribution and metabolism of PCM-CH2OH and PA-CH2OH were here clarified by analyzing plasma and tissues (liver, kidney, heart, lung, spleen and ovary) of female rats after single subcutaneous administration of [phenyl-14C]PCM-CH2OH and [phenyl-14C]PA-CH2OH at 62.5 mg/kg, respectively. In both rats dosed with PCM-CH2OH and PA-CH2OH, the radioactivity was similarly distributed into plasma and tissues, and PA-CH2OH was detected as the main metabolite in plasma, whereas PCM-CH2OH predominated in tissues except for kidney at 1 h after administration of PA-CH2OH. Furthermore, the cyclization ratio [PCM-CH2OH/(PCM-CH2OH+PA-CH2OH)] increased in tissues of PA-CH2OH dosed rats with passage of time. Both procymidone and PCM-CH2OH have convertible conformations (closed and open ring forms), so influence of pH conditions to their conversion was examined. Both compounds demonstrated closed rings under acidic conditions, and open rings under alkaline conditions. Generally, intracellar pH is kept at approximately neutral, and extracellular pH is kept at 0.6-0.7 units higher in all the animal species, so that our in vitro results supported in vivo findings.

Maternal exposure to anti-androgenic compounds, vinclozolin, flutamide and procymidone, has no effects on spermatogenesis and DNA methylation in male rats of subsequent generations.

To verify whether anti-androgens cause transgenerational effects on spermatogenesis and DNA methylation in rats, gravid Crl:CD(SD) female rats (4 or 5/group, gestational day (GD) 0=day sperm detected) were intraperitoneally treated with anti-androgenic compounds, such as vinclozolin (100 mg/kg/day), procymidone (100 mg/kg/day), or flutamide (10 mg/kg/day), from GD 8 to GD 15. Testes were collected from F1 male pups at postnatal day (PND) 6 for DNA methylation analysis of the region (210 bp including 7 CpG sites) within the lysophospholipase gene by bisulfite DNA sequencing method. F0 and F1 males underwent the sperm analysis (count, motility and morphology), followed by DNA methylation analysis of the sperm. Remaining F1 males were cohabited with untreated-females to obtain F2 male pups for subsequent DNA methylation analysis of the testes at PND 6. These analyses showed no effects on spermatogenesis and fertility in F1 males of any treatment group. DNA methylation status in testes (F1 and F2 pups at PND 6) or sperms (F1 males at 13 weeks old) of the treatment groups were comparable to the control at all observation points, although DNA methylation rates in testes were slightly lower than those in sperm. In F0 males, no abnormalities in the spermatogenesis, fertility and DNA methylation status of sperm were observed. No transgenerational abnormalities of spermatogenesis and DNA methylation status caused by anti-androgenic compounds were observed.

Metabolism of diethofencarb (isopropyl 3,4-diethoxyphenylcarbamate) in rats: identification of metabolites in urine.

Rats were orally given a diethofencarb (isopropyl 3,4-diethoxyphenylcarbamate) labeled with (14)C, at 300 mg/kg/day, for 4 consecutive days, and 11 metabolites in urine were purified by a combination of several chromatographic techniques. The chemical structures of all isolated metabolites were identified by spectroanalyses (NMR and MS). Ten of them were newly identified forms. Five of them were S-conjugates: three mercapturic acid conjugates, one S-methyl conjugate, and one SO-methyl conjugate. The others were two phenoxyacetic acids, hydroxyacetanilide, hydroxyisopropyl carbamate, and oxazolinone derivatives. From the results, the existence of the following reactions in rats can be concluded: (1) deethylation of the 4-ethoxy group; (2) conjugation of phenols with glutathione, gamma-glutamyltranspeptidation and depeptidation of the glutathione to form cysteine conjugates, and N-acetylation of the cysteine; (3) cleavage of the C-S linkage of cysteine conjugates followed by methylation; (4) oxidation of the S-methyl group; (5) cleavage of the carbamate linkage; (6) acetylation of the resultant amino group; (7) oxidation of the acetyl group; (8) oxidation of the isopropyl group; (9) cyclization of the oxidized isopropyl carbamate group; and (10) oxidation of the 4-ethoxy group.

(E)-2-(2-Hydroxyethylidene)-6-methyl-5-heptenal (alpha-acariolal) and (E)-2-(2-hydroxyethyl)-6-methyl-2,5-heptadienal (beta-acariolal), two new types of isomeric monoterpenes from Caloglyphus polyphyllae (Acari: Acaridae).

The opisthonotal gland secretion of the acarid mite, Caloglyphus polyphyllae, contained two new monoterpenes, (E)-2-(2-hydroxyethylidene)-6-methyl-5-heptenal (1) and (E)-2-(2-hydroxyethyl)-6-methyl-2,5-heptadienal (2), to which we have given the trivial names alpha- and beta-acariolal in relation to alpha- and beta-acaridial (3 and 4), respectively. Elucidation of the structure of 1 was established mainly from 1H-NMR and GC/MS spectral data after partial purification, together with the fact that 1 was recovered in the more-polar fraction from a silica gel column than alpha- and beta-acaridial (3 and 4) present in the secretion. Compound 2 was obtained in the same fraction as a mixture with 1. Based on the facts that 2 had the same molecular weight by GC/MS and the same polarity as that of 1, compound 2 was assumed to be a structural analog of 1. The structures of compounds 1 and 2 were confirmed by their synthesis in nine and ten respective steps starting from alpha-bromo-gamma-butyrolactone.

3-(4-Methyl-3-pentenyl)-2(5H)-furanone, alpha,alpha-acariolide and 4-(4-methyl-3-pentenyl)-2(5H)-furanone, alpha,beta-acariolide: new monoterpene lactones from the astigmatid mites, Schwiebea araujoae and Rhizoglyphus sp. (Astigmata: Acaridae).

A new monoterpene lactone from the acarid mite, Schwiebea araujoae, was elucidated without its isolation by GC/FT-IR and GC/MS analyses to be 3-(4-methyl-3-pentenyl)-2(5H)-furanone (1) and tentatively named as alpha,alpha-acariolide. The structure of 1 was identified by its synthesis from alpha-bromo-gamma-butyrolactone via 4 reaction steps. The synthesized compound gave the same GC/MS and GC/FT-IR spectra as those of the natural product. The other monoterpene lactone was likewise elucidated from the unidentified Rhizoglyphus mite to be 4-(4-methyl-3-pentenyl)-2(5H)-furanone (2) and named as alpha,beta-acariolide; it was also identified by its synthesis in 5 reaction steps from the same butyrolactone as the starting material. GC/MS and GC/FT-IR spectra of the preparation were identical to those of the natural product.