山莨菪碱对大鼠胸水中性白细胞花生四烯酸代谢的影响

本文研究了654-2对大鼠胸水中性白细胞代谢[1-¹⁴C]AA及内源性AA的影响。大鼠白细胞AA经5-LPO代谢途径形成的主要产物为LTB₄及5-HETE,经CO途径的主要产物为HHT及TXB₂。654-2对白细胞代谢[1-¹⁴C]AA无抑制作用,但显著减少白细胞从内源性AA形成的LTB₄,5-HETE,HHT及TXB₂。这种抑制作用与654-2呈剂量依赖关系。本实验结果表明,654-2抑制PG及LT的形成可能是影响了AA从胞膜的释放,而并非直接抑制CO及5-LPO。     

Selective inhibition of the cyclooxygenase pathway of the arachidonic acid cascade by the nonsteroidal antiinflammatory drug isoxicam

The effects of the nonsteroidal antiinflammatory drug isoxicam on prostaglandin formation by HSDM₁C₁ mouse fibrosarcoma cells grown in culture and 5-HETE(5(S)-5-hydroxy-6-trans, 8,11,14-cis eicosatetraenoic acid) formation by human leukocytes were determined. Isoxicam inhibited the formation of the cyclooxygenase product prostaglandin E₂ with an IC₅₀ of 2.0 μM. In comparison, the reference standards piroxicam and indomethacin had IC₅₀ values of 0.55 μM and 0.14 μM, respectively. Nordihydroguaiaretic acid (NDGA) was inactive up to 10 μM. Isoxicam, piroxicam, and indomethacin were relatively devoid of any significant inhibitory property on 5-lipoxygenase activity exhibiting IC₅₀ values > 500 μM. In comparison, the compounds BW755C and NDGA, known lipoxygenase inhibitors, had IC₅₀ values of 11 μM and 0.6 μM, respectively. The present findings indicated that isoxicam exhibited a selective inhibition of the cyclooxygenase pathway of the arachidonic acid cascade and that this effect may at least in part be responsible for its antiinflammatory activity observed in animals and humans.     

EFFECTS OF ORPANOXIN ON ARACHIDONIC ACID METABOLISM OF HUMAN POLYMORPHONUCLEAR LEUCOCYTES AND PLATELETS IN VITRO

1. The effect of orpanoxin, a nonsteroidal anti-inflammatory drug, on cyclooxygenase and lipoxygenase activity in human polymorphonuclear leucocytes (PMNL) and platelets was studied ex vivo to see if lipoxygenase inhibition contributed to orpanoxin's mechanism of action. 2. In PMNL, orpanoxin (50, 100, and 200 μmol/l), like indomethacin (100 μmol/l), had little effect on synthesis of leukotriene B₄ or 5S-hydroxy-6-trans,8,11,14-cis-eicosatetraenoic acid. BW755c at 100 μmol/l inhibited synthesis of both. 3. In PLT, orpanoxin (100 μmol/l) inhibited formation of cyclooxygenase products (thromboxanes, prostaglandins, and 12-l -hydroxy-5,8,10-heptadecatrienoic acid) and increased synthesis of the lipoxygenase product, 12S-hydroxy-5,8-cis, 10-trans,14-cis-eicosatetraenoic acid. Effects of indomethacin (100 μmol/l) and benoxaprofen (100 μmol/l) in platelets were qualitatively similar to those of orpanoxin. 4. These results indicate that the discrepancy between the low potency of orpanoxin in inhibiting bovine seminal vesicle cyclooxygenase in vitro and its high potency as an anti-inflammatory agent in vivo is not explained by its having an additional lipoxygenase inhibitory mechanism.     

Stimulation of 12-HETE production in human platelets by an immunomodulator, LF 1695. Evidence for activation of arachidonate liberation coupled to cyclo-oxygenase inhibition

Upon incubation with human platelets previously labelled with [14C]arachidonic acid, a new immunomodulator, LF 1695, induced the accumulation of [14C]-12-(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE). Although the time course of [14C]HETE accumulation was identical with 60 microM LF 1695 and calcium ionophore A23187, the latter compound also promoted the formation of 14C-labelled thromboxane B2 and 12-(S)-hydroxy-5,8,10-heptadecatrienoic acid (HHT), whereas 12-HETE was the only arachidonic acid metabolite generated under the action of LF 1695, suggesting that the drug inhibited cyclo-oxygenase. This was further confirmed by the fact that LF 1695 inhibited the second wave of platelet aggregation induced by ADP as well as arachidonic acid effects. Cell lipid analysis revealed that arachidonic acid was liberated from both triacylglycerol and phosphatidylcholine. The effect was observed in the concentration range 15-90 microM, with a half-maximal effect at 30 microM for HETE production, 15 microM for triacylglycerol hydrolysis and 45 microM for phosphatidylcholine deacylation. Incubation of platelets with [14C]arachidonic acid in the presence of 60 microM LF 1695 resulted in a strong inhibition of arachidonic acid incorporation into the various cell lipids, indicating that arachidonic acid mobilization might be due to inhibition of reacylation processes. It is concluded that LF 1695 displays an original and complex effect on platelet lipid metabolism, resulting in the specific generation of lipoxygenase metabolites.     

Phytochemical characterization and radical scavenger activity of flavonoids from Helichrysum italicum G. Don (compositae)

The glycosidic fraction of the flavonoids extracted from the flowering tops of the Helichrysum italicum G. Don was isolated, purified and characterized. This fraction was constituted by three compounds, which were assigned the structure of 4,2′,4′,6′-tetrahydroxychalcone-2′-glucoside, kaempferol-3-glucoside and naringenin-glycoside.Radical scavenger properties of the single glycosyl-flavonoids and of the in toto glycosidic fraction were tested with in vitro systems where different reactive oxygen species are generated (superoxide ions, hydroxyl radicals) and on lipid peroxidation induced by ADP/Fe²⁺ and NADPH or CCl₄ in rat liver microsomes. The formation of reactive oxygen species was detected by cytochrome c reduction, salicylic acid hydroxylation and hyaluronic acid depolymerization.The action of the glycosidic fraction on the release of TXB₂ and 12-HETE in human platelets, after collagen stimulation, was also evaluated.The glycosidic fraction inhibited in a dose dependent fashion lipid peroxidation in rat liver microsomes treated with ADP/Fe²⁺ or CCl₄. This effect is due to the ability of flavonoids to scavenge free radicals at different stages of the process (superoxide ions, hydroxyl and lipid peroxide radicals). The single glycosylflavonoids exhibited a different scavenger activity, depending on the oxygen species and the chemical structure of the compounds. No effect of the fraction was observed on TXB₂ and 12-HETE formation at 100 μm concentration.     

A study of the novel anti-inflammatory agent florifenine topical anti-inflammatory activity and influence on arachidonic acid metabolism and neutrophil functions

We have evaluated the effects of the novel anti-inflammatory agent florifenine, 2-(1-Pyrrolidinyl)ethyl N-[7-(trifluoromethyl)-4-quinolyl]anthranilate, on topical inflammation in mice, free radical-mediated reactions, arachidonic acid metabolism and some neutrophil functions. Topical administration of florifenine produced dose-related anti-inflammatory activity in 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ear oedema and with a lower potency, in the response induced by arachidonic acid (AA). Florifenine also inhibited neutrophil migration and PGE₂ content in the inflammed ears. In human whole blood, florifenine was a potent and selective inhibitor of TXB₂ generation. This anti-inflammatory agent did not exert antioxidant effects but inhibited elastase release in human neutrophils without affecting superoxide anion generation. Florifenine administration to mice dose-dependently inhibited leukocyte migration and PGE₂ levels in the air pouch inflammation induced by zymosan. These results demonstrate the topical anti-inflammatory activity of florifenine and provide a basis for understanding the mechanisms involved in the inhibitory effects of this agent on inflammatory responses.     

In vivo and in vitro effects of nafazatrom (Bay g 6575), an antithrombotic compound,on arachidonic acid metabolism in platelets and vascular tissue

Nafazatrom, given acutely to male volunteers, had no effect on platelet aggregation, associated thromboxane B₂ (TXB₂) formation or the evaluated hormonal, renal and cardiovascular parameters. Only slight increases in plasma levels of 6-keto-PGF_1α and in platelet counts were observed. However, a marked influence of nafazatrom on arachidonic acid metabolism in certain in vitro systems was found. Prostaglandin synthesis by rabbit kidney cortex microsomes was significantly enhanced, PGI₂ being stimulated the most. In normal human platelets arachidonic acid metabolism was not influenced significantly by nafazatrom which was taken up by the platelets in a dose-dependent manner. In contrast, in platelets with a high peroxide level probably due to depletion of reducing cofactors, 12-hydroperoxy-eicosatetraenoic acid was transformed to 12-hydroxy-eicosatetetraenoic acid by nafazatrom, while the formation of TXB₂ was stimulated. These findings suggest that nafazatrom may act as a reducing cofactor for the hydroperoxidase involved in the cyclooxygenase- and lipoxygenase-pathways of arachidonic acid metabolism.     

Inhibition of fatty acid oxygenases by onion and garlic oils: Evidence for the mechanism by which these oils inhibit platelet aggregation

Inhibition of in vitro platelet aggregation by onion and garlic oils was accompanied by decreased formation of thromboxane B₂ (TXB₂) and 12-hydroxyheptadecatrienoic acid (HHT) from [1-¹⁴C]arachidonic acid (AA). At intermediate concentrations (10–30 $\text{μg}\text{ml}$), these oils also induced a redistribution of the products of the lipoxygenase pathway; at higher concentrations (30–60 $\text{μg}\text{ml}$), they completely suppressed the formation of all oxygenase products. Measurements of oxygen consumption in antimycin-treated platelets indicated a direct correlation between inhibition of platelet fatty acid oxygenases and the anti-aggregating activity of these oils. Onion and garlic oils also inhibited fatty acid oxygenases from sheep vesicular gland preparations as shown both by decreased oxygen consumption and decreased formation of prostaglandin E₂ (PGE₂) and PGD₂ from [1-¹⁴C]AA. Onion oil was approximately ten times more effective in inhibiting the platelet oxygenases than the oxygenases from the vesicular gland. In addition, these oils suppressed the soybean lipoxygenase-catalyzed oxygenation of AA. In all three enzyme systems, onion oil exhibited greater inhibitory activity than garlic oil. Many nonsteroidal anti-inflammatory and anti-thrombotic drugs act by inhibiting the cyclooxygenase component of the prostaglandin and thromboxane synthetases. Our findings thus suggest that onion and garlic contain compounds that may have serendipitous pharmacological effects.     

Derivatives of 2-Amino-1,2,3,4-Tetrahydronaphthalene,VIII.1) Isomerization of trans-2-Acetamido-3-hydroxy-5,8-dimethoxy-1,2,3,4-tetrahydronaphthalene and Hydrolysis of 5,8-Dimethoxy-2-methyl-3a,4,9,9a-tetrahydronaphth[2,3-d]oxazoline Hydrochloride

The isomerization of trans-2-acetamido-3-hydroxy-5,8-dimethoxytetraline (1) under the action of hydrogen chloride was investigated. Hydrolysis of 5,8-dimethoxy-2-methyl-3a,4,9,9a-tetrahydronaphth[2,3-d]oxazoline hydrochloride (2) leads to cis-2-amino-3-hydroxy-5,8-dimethoxytetraline (3) .     

山莨菪碱对洗涤大鼠血小板代谢花生四烯酸的影响

作者建立了一个用大鼠洗涤血小板研究药物对外源性及内源性AA代谢影响的方法。采用HPLC测定血小板AA代谢物HHT及12-HETE,观察了底物(AA)浓度、孵育时间、A23187加量等对血小板代谢AA的影响。并用此法研究了654-2对洗涤血小板AA代谢的影响。654-2显著减少血小板从内源性AA形成HHT及12-HETE,且作用随剂量增加而增强,但不影响血小板对外源性AA的代谢。上述结果表明,654-2是通过抑制AA释放而减少AA代谢物的形成。     

Stimulation of human airway epithelial cells by platelet activating factor (PAF) and arachidonic acid produces 15-hydroxyeicosatetraenoic acid (15-HETE) capable of contracting bronchial smooth muscle

Human airway epithelial cells grown to confluence were incubated with varying concentrations (10–100 μM) of arachidonic acid or platelet activating factor (PAF) for periods of 30 min to 24 h. Both stimuli caused the production of 15-hydroxyeicosatetraenoic acid (15-HETE) by epithelial cells as determined by HPLC. Neither stimulus caused the production of leukotrienes, thromboxane or prostaglandins aside from minimal amounts of PGE₂. Maximal production of 15-HETE after arachidonic acid (10 μM; N = 9) occurred at 1 h (235±59 ng/mg protein), whereas maximum generation after PAF treatment (10 μM; N = 9) occurred at 6 h (153±48 ng/mg protein). Neither arachidonic acid nor PAF at concentrations up to 100 μM caused cell toxicity as determined by ⁵¹Cr release. 15-HETE at concentrations of ≥0.1 μM contracted isolated human bronchus. An initial small amplitude, short-lasting (< 15 min) contraction was followed by a much larger contraction beginning 30–60 min following 15-HETE challenge, reaching a maximum at ~ 2 hr. These results demonstrate that PAF may induce delayed airway smooth muscle contraction by the generation of 15-HETE from epithelial cells. The kinetics of 15-HETE generation and its contractile activity are compatible with it being a mediator of the late asthmatic reaction.     

Polychlorinated biphenyls induce arachidonic acid release in human platelets in a tamoxifen sensitive manner via activation of group IVA cytosolic phospholipase A2-alpha

Polychlorinated biphenyls (PCBs) are stable compounds commonly found in nature as environmental pollutants. PCBs can affect the endocrine function of hormones such as steroid-hormones. Also, PCBs are known to be inducers of arachidonic acid release in various cells. We report, here, the effects of PCBs on eicosanoid formation, arachidonic acid release and cytosolic phospholipase A2-alpha (cPLA2-alpha) activation in human platelets. Ortho-substituted PCBs induced a time and dose-dependent release of arachidonic acid and the concomitant formation of 12(S)-hydroxy-5,8-cis-10-trans-14-cis-eicosatetraenoic acid (12-HETE) and 12(S)-hydroxy-5-cis-8,10-trans-heptadecatrienoic acid (12-HHT) in human platelets. The release of arachidonic acid and the formation of 12-HETE was completely blocked by the cPLA2-alpha inhibitors AACOCF3 or pyrrolidine-1. PCB-treatment of platelets demonstrated that the cPLA2-alpha protein as well as PLA2 activity translocated to the membrane fraction, independent of a rise in intracellular Ca2+. Furthermore, electrophoretic gel mobility shift analysis of cPLA2-alpha on SDS-PAGE demonstrated a PCB-dependent phosphorylation of cPLA2-alpha. The effects of 17beta-estradiol and two structurally unrelated anti-estrogens, nafoxidin and tamoxifen on PCB-induced arachidonic acid release in platelets were also investigated. Both nafoxidin and tamoxifen inhibited PCB-induced arachidonic acid release as well as 12-HETE and 12-HHT formation. Interestingly, platelets incubated with PCBs did not aggregate despite the fact that robust release of arachidonic acid was observed. In summary, these results demonstrate that certain PCBs induce activation of cPLA2-alpha independent of a rise in intracellular calcium and a robust release of arachidonic acid release with resulting eicosanoid formation in human platelets.     

Chromone glycosides from Knoxia corymbosa

Four new chromone glycosides, corymbosins K₁-K₄ (3–6), together with two known compounds, noreugenin (1) and undulatoside A (2), were isolated from the whole plant of Knoxia corymbosa (Rubiaceae). The structures of the new compounds were established through extensive NMR or X-ray spectroscopic analysis as 7-O-β-d-allopyranosyl-5-hydroxy-2-methylchromone (corymbosin K₁, 3), 7-O-β-d-6-acetylglucopyranosyl-5-hydroxy-2-methylchromone (corymbosin K₂, 4), 7-O-[6-O-(4-O-trans-caffeoyl-β-d-allopyranosyl)]-β-d-glucopyranosyl-5-hydroxy-2-methylchromone (corymbosin K₃, 5) and 7-O-[6-O-(4-O-trans-feruloyl-β-d-allopyranosyl)]-β-d-glucopyranosyl-5-hydroxy-2- methylchromone (corymbosin K₄, 6). Compounds 2–5 were subjected to test their immunomodulatory activity in vitro.     

Mechanism of Action of p-Chlorobiphenyl on the Inhibition of Platelet Aggregation

p-Chlorobiphenyl (1–50 μm ) concentration-dependently inhibited the aggregation and release reaction of rabbit washed platelets induced by arachidonic acid and collagen, but not those induced by platelet-activating factor (PAF), U46619 and thrombin. The IC50 values of p-chlorobiphenyl on the arachidonic acid and collagen-induced platelet aggregation were 2.9 ± 0.5 and 12.8 ± 2.3 μm , respectively. The formation of both platelet thromboxane B₂ and prostaglandin D₂ caused by arachidonic acid was inhibited by p-chlorobiphenyl concentration-dependently. In myo-[³H]inositol-labeled and fura-2-loaded platelets, [³H]inositol monophosphate generation and the rise in intracellular Ca²⁺ stimulated by arachidonic acid were inhibited by p-chlorobiphenyl. In human platelet-rich plasma, p-chlorobiphenyl and indomethacin prevented the secondary aggregation and blocked ATP release from platelets induced by adenosine 5′-diphosphate and adrenaline without affecting the primary aggregation. It is concluded that p-chlorobiphenyl may be a cyclo-oxygenase inhibitor and its antiplatelet action is mainly due to the inhibition of thromboxane formation.     

Increased metabolism of arachidonic acid in an immune model of colitis in guinea-pigs.

Inflammation of the guinea-pig colon was produced by skin sensitization and subsequent intracolonic challenge with the chemical hapten, dinitrochlorobenzene. Metabolism of [14C]-arachidonic acid by homogenates of control colon was very low, although metabolites co-migrating on thin layer chromatography (t.l.c.) with prostaglandin E2 (PGE2), PGF2 alpha, PGD2, 6-keto-PGF1 alpha, thromboxane B2 (TXB2), HHT and 11-, 12-, 15-HETE were formed. There was an overall 3 fold increase in metabolism of [14C]-arachidonic acid by homogenates of inflamed mucosa. The greatest increase in metabolite formation was of PGE2, with smaller increases in HHT, 11-, 12-, 15-HETE, PGD2, TXB2, PGF2 alpha and 6-keto-PGF1 alpha. The formation of these metabolites was inhibited both by indomethacin and the dual pathway inhibitor, BW755C. The formation of immunoreactive PGE2, TXB2 and 6-keto-PGF1 alpha was also increased in homogenates of inflamed guinea-pig colon. The small level of immunoreactive LTB4 detected in control colon was not changed in inflamed colonic tissue. The dinitrochlorobenzene model of colitis offers a means of studying arachidonic acid metabolism in an immune-mediated inflammatory response in intestinal tissue.     

16(R)-hydroxy-5,8,11,14-eicosatetraenoic acid, a new arachidonate metabolite in human polymorphonuclear leukocytes

Intact human polymorphonuclear leukocytes (PMNL) incubated with substimulatory amounts of arachidonic acid in the absence of a calcium ionophore formed four metabolites that were isolated by reverse-phase HPLC and characterized structurally by GC/MS. A major metabolite eluting as the most abundant peak of radioactivity lacked UV chromophores above 215 nm, and its formation was sensitive to 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF525A) but not 3-amino-1-[m(trifluoromethyl)phenyl]-2-pyrazoline (BW755C), suggesting that it was likely to be a product of cytochrome P450. The GC/MS analysis revealed the presence of two components: 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) and 16-hydroxy-5,8,11,14-eicosatetraenoic acid (16-HETE) in an approximate ratio of 4:1. The minor metabolites were identified as 15-HETE and 5-HETE. Although 20-HETE has been observed previously as a product of arachidonic acid metabolism in PMNL, the occurrence of 16-HETE was a novel finding. The stereochemistry of the hydroxyl group in PMNL-derived 16-HETE was established by analysis of 1-pentafluorobenzyl-16-naphthoyl derivatives on a chiral-phase chromatographic column and comparison with authentic synthetic stereoisomers. The PMNL-derived radioactive metabolite co-eluted with the synthetic 16(R)-HETE stereoisomer. Analysis of the total lipid extracts from intact PMNL followed by mild alkaline hydrolysis resulted in detectable amounts of 16-HETE (108+/-26 pg/10(8) cells) and 20-HETE (341+/-69 pg/10(8) cells), which suggested that these HETEs were formed from endogenous arachidonic acid and esterified within PMNL lipids. Thus, in contrast to calcium ionophore-stimulated neutrophils that generate large amounts of 5-lipoxygenase products, the intact PMNL generate 20-HETE and 16(R)-HETE via a cytochrome P450 omega- and omega-4 oxygenase(s).     

Respiratory effects produced by microinjection of -glutamate and an uptake inhibitor of -glutamate into the caudal subretrofacial area of the medulla

The purposes of our study were to determine the type of respiratory changes that would occur when either an excitatory amino acid receptor agonist or an uptake inhibitor was administered into the caudal subretrofacial area. This was done by microinjecting either -glutamate or -pyrrolidine-2,4-dicarboxylate ( -trans-2,4-PDC) into the caudal subretrofacial area while monitoring tidal volume, respiratory rate, mean arterial blood pressure and heart rate. Bilateral microinjection of 2.5 nmol of -glutamate into the caudal subretrofacial area produced apnea in eight of eight animals tested, and the duration of apnea was 27 ± 2 s. To determine the type of -glutamate receptor responsible for mediating the apneic response, antagonists of the N-methyl- -aspartate (NMDA) and non-NMDA receptor, namely, 3-[(RS)-carboxypiperazin-4-yl]-propyl-phosphonic acid (CPP), and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), respectively, were tested. Neither antagonist in doses that blocked NMDA (in the case of CPP) and amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) (in the case of CNQX) blocked apnea elicited by -glutamate. In addition, kynurenic acid, an antagonist of NMDA and non-NMDA ionotropic receptors, failed to block the effect of -glutamate. Microinjection of the metabotropic receptor agonist drug, trans- -1-amino-1,3-cyclopentone-dicarboxylic acid ( -trans-ACPD), into the caudal subretrofacial area failed to have any effect on respiratory activity. Because of the inability to block the effect of -glutamate in the caudal subretrofacial area, and the lack of effect of -trans-ACPD, the data suggest that the apneic response produced by -glutamate is mediated by an as yet undefined receptor. Microinjection of the -glutamate uptake inhibitor, -trans-2,4-PDC, was found to produce apnea. Using the dose of 0.5 nmol of -trans-2,4-PDC, we examined the type of excitatory amino acid receptor that mediated the response. Neither pretreatment with the NMDA receptor antagonist, CPP, nor the non-NMDA receptor antagonist, CNQX, affected -trans-2,4-PDC-induced apnea. However, combined use of these two antagonists prevented -trans-2,4-PDC-induced apnea. These data suggest that the effect of synaptically released exitatory amino acid at the caudal subretrofacial area on breathing is apnea, and that this effect is mediated by simultaneous activation of both NMDA and non-NMDA ionotropic receptors.     

Zur Totalsynthese des 5-Acetoxy-6-methoxykawains

Total Synthesis of 5-Acetoxy-6-methoxykawain The oxidation of 5-hydroxy-4-methoxy-6-trans-styryl-2H-pyran-2-one ( 6 ) by periodic acid in methanol gives rise to racem.-4,6-dimethoxy-6-trans-styryl-2,5-pyrandione ( 7 ). The yield is 35% Compound 7 is the key intermediate¹⁾ for the total synthesis of (5S, 6S)-(+)-acetoxy-4,6-dimethoxy-6-trans-styryl-5,6-dihydro-2H-pyran-2-one ( 1 ).     

The toxicity and metabolism of the pyrethroids cis-and trans-cypermethrin in rainbow trout,Salmo gairdneri

1. The toxicity of cis-and trans-cypermethrin to rainbow trout was investigated and the concentrations of the two isomers in brain associated with toxic signs (excitability and loss of equilibrium) were determined. cis-Cypermethrin and trans-cypermethrin were equally toxic and showed similar brain levels associated with toxic signs (cis:0.25 μg/g, mean (range 0.07-0-53); trans:0.17 μg/g (0-07-0-31)).

2. Orally administered cypermethrin was less toxic than predicted, probably due to poor intestinal uptake. Toxicity was due to absorption via the gills of unchanged pyrethroid excreted from the intestine into the water.

3. The metabolism of the radiolabelled insecticides, [¹⁴C-cyclopropyl]- and [¹⁴C-benzyl]-cis- and trans-cypermethrin has been investigated in vivo and in vitro.

4. The principal route of elimination in vivo was the bile, with 20-28% dose excreted as biliary metabolites in 24h. No difference in the rates of elimination of the cis and trans isomers was observed.

5. cis-Cypermethrin was metabolized primarily to the glucuronide of 4′-hydroxy-cypermethrin (80% total bile radioactivity), together with dichlorovinyldimethyl-cyclopropanecarboxylic acid and its glucuronide, 3-(4-hydroxyphenoxy)benzoic acid (4′-hydroxy-3BPA) and its ester and ether glucuronides, 3-phenoxybenzoyl glucuronide and 4′-hydroxy-3BPA sulphate were detected. trans-Cypermethrin was metabolized to the same products, but with only 36% as 4′-hydroxy-cypermethrin glucuronide.