Norio Kurihara

Studies on BHC isomers and related compounds V. Some physicochemical properties of BHC isomers (1)

Abstract Physicochemical properties of biological interest were measured for hexachlorocyclohexane (benzene hexachloride) isomers, including solubility in water and in aqueous protein solutions, partition coefficients between organic solvents and water, and some “adsorption equilibrium” constants between the macromolecules and water. Some of the properties show a correlation with the free energy-related hydrophobic parameter “π”.

Oxidative metabolism of lindane and its isomers with microsomes from rat liver and house fly abdomen

Abstract Lindane and other hexachlorocyclohexane isomers produced 2,4,6-trichlorophenol as the major oxidative metabolite when incubated in the presence of NADPH under aerobic condition. A mechanism for the formation of 2,4,6-trichlorophenol is proposed, which includes direct oxygenation of the cyclohexane ring. The proposed mechanism is supported by data from studies of model chemical reactions of the pentachlorocyclohexanol isomers. Pathways leading to 1,2,4-trichlorobenzene, tetrachlorobenzene isomers, 2,4,5-trichlorophenol, and tetrachlorophenol isomers are discussed, and are considered to include the route through pentachlorocyclohexene and hexachlorocyclohexene. Reductive dechlorination of lindane under anaerobic condition was observed using microsomes and NADPH.

Oxidative metabolism of tetrachlorocyclohexenes, pentachlorocyclohexenes, and hexachlorocyclohexenes with microsomes from rat liver and house fly abdomen☆

Abstract Microsomal mixed-function oxidase systems from rat liver and house fly abdomen effectively metabolized isomers of 3,4,5,6-tetrachlorocyclohexene, 1,3,4,5,6-pentachlorocyclohexene, and 1,2,3,4,5,6-hexachlorocyclohexene to tetrachlorocyclohexenol isomers, 2,4,5,-trichlorophenol, and 2,3,4,6-tetrachlorophenol, respectively. The ( 346 5 )-isomer of pentachlorocyclohexene gave also an abundant amount of pentachlorocyclohexenol isomers. As the metabolites of ( 36 45 )-, ( 35 46 )-, and ( 34 56 )-hexachlorocyclohexene , some compounds such as 1,2,4-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, and pentachlorobenzene were more abundantly formed, respectively, than 2,3,4,6-tetrachlorophenol. These oxidative metabolic reactions were shown to mainly proceed via “ene-like” hydroxylation accompanied by double bond migration. Inhibition by CO, piperonyl butoxide, and SKF 525-A suggested that the “ene-like” hydroxylating enzyme was cytochrome P -450 dependent. The formation of an isomer of pentachlorocyclohexenol from ( 36 45 )-hexachlorocyclohexene was also observed, and this reaction was activated by SKF 525-A.

Metabolism of lindane in house flies: Metabolic desaturation, dehydrogenation and dehydrochlorination, and conjugation with glutathione

Abstract In lindane-treated house flies, a cis-dehydrogenated metabolite, ( 36 45 )- hexachlorocyclohexene , was identified by gas-liquid chromatography and mass spectrometry. The in vitro metabolism study showed that in the presence of NADPH the microsomal fraction of house flies converted lindane to three hexane-soluble metabolites. This conversion was inhibited by piperonyl butoxide, SKF-525A, and carbon monoxide. These metabolites were identified as ( 36 45 )- hexachlorocyclohexene , ( 36 45 )- and ( 346 5 )-pentachlorocyclohexene (PCCHE) by gas-liquid chromatography. They, as well as lindane, were excellent substrates for the reaction with the postmicrosomal fraction in the presence of glutathione. While the reaction with lindane-d6 showed a significant deuterium isotope effect (6.82), that of ( 36 45 )- PCCHE-d 5 did not (1.18). Enzymatic conjugation with glutathione probably occurs at the stage of PCCHE.

Mercapturic acid formation from lindane in rats

Abstract 4-Chloro-, 2,4-dichloro-, 3,4-dichloro-, 2,3,5-trichloro-, and 2,4,5-trichlorophenylmercapturic acids were identified as main metabolites of lindane, γ-isomer of 1,2,3,4,5,6-hexachloro-cyclohexane, in rat urine. Pathways to these metabolites were shown to include ( 36 45 )- hexachlorocyclohexene as the most important intermediary metabolite. ( 346 5 )- Pentachlorocyclohexene and ( 346 5 )- tetrachlorocyclohexene also seem to be involved in these pathways, while ( 36 45 )- pentachlorocyclohexene plays a minor role in the pathway. Glutathione conjugation, using the rat liver soluble fraction, occurred directly on the polychlorocyclohexenes, not on their further transformed products. In in vivo biodegradation, ( 36 45 )- hexachlorocyclohexene may be dechlorinated and dehydrochlorinated at the endoplasmic reticulum before it undergoes the glutathione conjugation in cytosol, although other polychlorocyclohexenes generally react in a manner similar to that in the in vitro reaction.

Inhibitory effects of BHC isomers on Na+-K+-ATPase, yeast growth, and nerve conduction

Abstract The biological effects of benzene hexachloride (BHC, 1,2,3,4,5,6-hexachlorocyclohexane) isomers, such as toxicity against yeasts, inhibition of beef brain Na + -K + -ATPase, and blocking action on conduction in cockroach nerve, were determined and compared with those shown by homologous alcohols and other molecules. Each type of biological activity correlated well with the physicochemical properties of the test compounds such as hydrophobicity (as defined by their partition coefficients in 1-octanol/H 2 O). The insecticidal action of γ-BHC showed little correspondence to Na + -K + -ATPase inhibition or to nerve blocking in insects.

Promotion of norepinephrine release and inhibition of calcium uptake by pyrethroids in rat brain synaptosomes

Abstract A series of 25 pyrethroids were assessed for their effects on Na + -dependent norepinephrine release and on Ca 2+ uptake in vitro using a crude rat brain synaptosomal preparation. The most effective pyrethroids required a concentration of 3–10 μ M to promote norepinephrine release. Plotting release data versus lipophilicity (as log P ) for each compound resulted in a parabolic curve with log P opt being 5.4 for maximal release. The release promoted by most of the compounds assessed at 30 μ M could not be or was only partially reversed by either tetrodotoxin or substituting choline for Na + conditions which readily reversed the release promoting effects of veratridine. Thus, many pyrethroids, particularly those without the α-cyano group, did not display their expected effects on the Na + channel in rat brain. When assessed at 5 μ M , pyrethroids inhibited, had no effect, or caused increases in the amount of Ca 2+ incorporated in the presence of ATP. The effectiveness of the various pyrethroids to inhibit Ca 2+ uptake again displayed a parabolic relationship with log P opt being 6.4. It was concluded that the variations in pyrethroid effects on norepinephrine release and Ca 2+ uptake are not solely related to their particular chemical structures, but to lipophilicity. The effects of many pyrethroids on Ca 2+ metabolism, particularly displacement of bound Ca 2+ , better explain the transmitter release promoting properties in vitro rather than a direct effect on the Na + channel. No direct relationship between known toxicity to mammals and Ca 2+ inhibition by pyrethroids was established.

The mechanism of resistance to lindane and hexadeuterated lindane in the Third Yumenoshima strain of house fly

Abstract The factors which cause lindane resistance in the Third Yumenoshima strain, a strain of house flies highly resistant to insecticides, were studied using hexadeuterated lindane. Hexadeuterated lindane has the same physicochemical properties as lindane, but the former is much less biodegradable than the latter. The LD 50 ratio of lindane to hexadeuterated lindane in this strain, deuterium isotope effect on LD 50 values, was larger than that in S NAIDM , a susceptible (nonresistant) strain. The penetration rates of labeled and nonlabeled lindane through the insect cuticle were about the same for both strains. Thus, penetration rate does not cause resistance. The metabolic degradation of lindane in the resistant strain in vivo occurred much faster than in the susceptible strain. This was also the case for lindane degradation processes in vitro such as microsomal oxidation and glutathione conjugation. In both strains, significant isotope effects were observed in the degradation rates in vitro of labeled and nonlabeled lindane. Therefore, principal biodegradation and detoxication pathways should include reactions which cleave the CH bonds. When the much less biodegradable d 6 counterpart of lindane was applied to both strains, the susceptible strain became much more highly intoxicated than the other within 20 to 30 min. This indicates that a combination of both greater degradability and probably lower sensitivity at the action site are the main factors underlying resistance in the Third Yumenoshima strain.

ATP synthesis associated with the conversion of hexachlorocyclohexane related compounds

Clostridium rectum strain S-17 converts γ-1,2,3,4,5,6-hexachlorocyclohexane (HCH) related compounds to chlorobenzenes. The metabolites from γ-1,2,3,4,5,6-hexachlorocyclohexene and γ-1,3,4,5,6-pentachlorocyclohexene are identified as 1,2,4-trichlorobenzene and 1,4-dichlorobenzene, respectively. ATP synthesis, converting these chlorinated compounds, is observed in the cell suspension of C. rectum as indicated by luciferase-luciferin reaction and phosphorylation of 32P-labeled phosphate. These observation lead to the conclusion that HCH and related compounds serve as artificial electron acceptors of the Stickland reaction, and therefore, the reductive dechlorination is associated with ATP synthesis.

Activity of ecdysone analogs in enhancing N-acetylglucosamine incorporation into the cultured integument of Chilo suppressalis

Ecdysone analogs with various side chains at the 17-position of the steroid structure enhanced the incorporation of N-acetylglucosamine as 20-hydroxyecdysone into the cultured integument prepared from Chilo suppressalis. Their activity in terms of the concentration required to give 50% of the maximum response varied with the structure. Piperonyl butoxide, an inhibitor of oxidation metabolism, did not enhance the in vitro effect of the compounds. The order of potency was ponasterone A > 20-hydroxyecdysone > cyasterone > inokosterone > makisterone A >> ecdysone.