Single administration toxicokinetic studies of decalin (decahydronaphthalene) in rats and mice.

Decalin (decahydronaphthalene) is an industrial solvent known to cause alpha2u-globulin nephropathy in male rats. Studies were conducted using decalin (mixture of cis and trans isomers) to (1) characterize systemic elimination of decalin in rats and mice and (2) evaluate disposition of decalin, its metabolites, and kidney alpha2u-globulin in young and old rats of both sexes following a single 6-h whole-body inhalation exposure at up to 400 ppm decalin. Additionally, a separate group of young male F344/N rats were administered either cis- or trans-decalin iv at doses up to 20 mg/kg to assess disposition of each isomer, its metabolites, and kidney alpha2u-globulin. Decalin was eliminated from blood in a dose-dependent manner, regardless of sex, age, or species. C0 and AUC infinity increased supra-proportionally with exposure concentration. Mice were more efficient in eliminating decalin than rats at lower exposure concentrations, but nonlinear elimination kinetics were more noticeable at 400 ppm. Sex differences in blood decalin elimination were observed in rats; females had a consistently higher AUC infinity at all exposure concentrations. There was a dose-dependent increase in kidney decalin, decalone, and alpha2u-globulin in male rats exposed to decalin. Kidney alpha2u-globulin and decalone concentrations in old male rats were substantially lower than those in young males, but were similar to those observed in all (young and old) females. Compared to old males and all females, young male rats had significantly lower urinary decalol concentrations, but higher kidney decalin, decalone, and alpha2u-globulin concentrations. Administration of decalin to male rats as either the cis or trans isomer revealed that more cis -decalone is produced per unit dose as compared to trans-decalone, and that more trans-decalin accumulated in the kidney (as alpha2u-globulin-ligand complexes) compared to cis-decalin. These patterns of isomer-specific metabolism were also reflected in the cis/trans ratios of decalin in blood, as well as urinary decalol metabolites. The ratio of alpha2u-globulin to the total amount of decalin plus decalone measured in the male rat kidney was approximately 1.0. Therefore, alpha2u-globulin was a key factor in the accumulation of decalin and decalone in kidneys of young male rats, decalin and decalone were practically absent in all females and in old males.     

The metabolism of t-butylcyclohexane in Fischer-344 male rats with hyaline droplet nephropathy

The molecule t-butylcyclohexane is one of the first examples of a branched alkyl group attached to a hydrocarbon ring shown to be capable of producing renal damage at the corticomedullary junction of male rats. A metabolic study of t-butylcyclohexane yielded the following urinary metabolites: trans-4-t-butylcyclohexanol, 2c-hydroxy-4t-t-butylcyclohexanol, 2-methyl-2-cyclohexylpropanoic acid, 2c-hydroxy-4c-t-butylcyclohexanol, 2-methyl-2-cyclohexyl-1,3-propanediol, 2t-hydroxy-4t-t-butylcyclohexanol, and cis -4-t-butylcyclohexanol. As with other hydrocarbons of similar molecular weight that induce nephropathy in male rats, preferential sites of oxidative metabolism were observed that could potentially be related to the pathogenesis.     

Synthesis and evaluation of substituted 2-phenylcyclobutylamines as analogues of hallucinogenic phenethylamines: lack of LSD-like biological activity

cis- and trans-2-(2,4,5-trimethoxyphenyl)cyclobutylamine and trans-2-(2,5-dimethoxy-4-methylphenyl)cyclobutylamine were synthesized as conformationally restricted analogues of hallucinogenic phenylisopropylamines. In rats trained to discriminate saline from LSD (0.08 mg/kg, ip) in a two-lever drug discrimination paradigm, no generalization of the LSD stimulus to the cis trimethoxy compound occurred at doses up to 20 mg/kg. For both of the trans compounds, partial generalization of the LSD cue occurred at doses of 5 mg/kg or greater. In contrast, complete generalization occurred with trans-2-(2,5-dimethoxy-4-methylphenyl)cyclopropylamine. The ED50 for this compound and the doses of the trans cyclobutyl homologues at which significant drug-appropriate responding occurred indicate that the latter are on the order of 50-75 times less potent than the cyclopropylamine analogue. The lack of generalization to the cyclobutylamines indicates either that their discriminative stimulus properties differ from LSD or that they lack discriminative effects.     

Synthesis and biological activities of ftorafur metabolites. 3'- and 4'-hydroxyftorafur.

Four isomers of ftorafur were synthesized as authentic samples of possible ftorafur (FT) metabolites. 2,3-Dihydrofuran was treated with perbenzoic acid in MeOH to give 2-methoxy-3-hydroxytetrahydrofuran, which upon treatment with Ac2O/pyridine yielded the key intermediate 2-methoxy-3-acetoxytetrahydrofuran. The other intermediate, 2-ethoxy-4-acetoxytetrahydrofuran, was prepared by acid hydrolysis (HCl/50% EtOH) of 1,1-diethoxy-3,4-dihydroxybutane, followed by acetylation (Ac2O/pyridine). Treatment of 2,4-bis(trimethylsilyl)-5-fluorouracil with either 2-methoxy-3-acetoxytetrahydrofuran or 2-ethoxy-4-acetoxytetrahydrofuran in 1,2-dichloroethane at room temperature using SnCl4 as catalyst afforded cis- and trans-3'-OAc-FT or 4'-OAc-FT, respectively. However, trans-3'-OAc-FT and cis-4'-OAc-FT were the major condensation products. In each case, separation of these cis and trans isomers was achieved by silica gel column chromatography. Treatment of 3'- or 4'-OAc-FT with NH3/CH3OH at 5 degrees C overnight yielded the described hydroxylated FT. Both trans-3'-OH-FT and cis-4'-OH-FT showed no significant activity against L1210 up to 100 mg/kg. These two agents produced an inhibitory effect on HeLa cell growth equal to that of ftorafur, with ID50 = 200 MICROGRAMS/KG.     

Quinuclidine chemistry. 4. Diuretic properties of cis-3-amino-2-benzhydrylquinuclidine.

A number of 3-amino-2-benzhydrylquinuclidines were tested for diuretic activity in both rats and dogs. The Schiff base formed from 2-benzhydryl-3-quinuclidinone and benzylamine was reduced with NaBH4 to a mixture of isomers, the cis isomer being preponderants. cis-2-Benzhydryl-3-benzylaminoquinuclidine was isolated by chromatography and debenzylat:d to cis-3-amino-2-benzhydrylquinuclidine, the most active compound in this series. The corresponding trans isomer was considerably less active. It was made by reacting the mesylate of cis-2-benzhydr-l-3-quinuclidinol with Nan3 to form trans-3-azido-2-benzhydrylquinuclidine which was reduced with LiAlH4. In dose-response studies (sodium excretion as a function of dose) in rats the maximal or ceiling effect of cis-3-amino-2-benzhydrylquinuclidine was considerably greater than that of hydroflumethiazide but less than that of furosemide. An unusual biphasic dose-response was seen in dogs with cis-3-amino-2-bezhydrylquinuclidine, centering around 10 mg/kg.     

Alpha 2u-globulin nephropathy and carcinogenicity following exposure to decalin (decahydronaphthalene) in F344/N rats.

Decalin (decahydronaphthalene) is a widely used industrial solvent known to cause male rat-specific alpha2u-globulin nephropathy. In this project, 13-week and two-year inhalation studies of decalin were conducted consecutively in both sexes of F344/N rats. The key objectives were to (1) characterize the 13-week toxicity of decalin in rats, with an emphasis on nephropathy in males; (2) compare the kidney concentrations of decalin, 2-decalone, and alpha2u-globulin in males over 2 to 13 weeks of decalin exposure; and (3) correlate male rat nephropathy observed in the 13-week study with renal carcinogenicity in the two-year study. F344 rats (M/F) were exposed via whole-body inhalation to 0, 25, 50, 100, 200, or 400 ppm decalin for 13 weeks. Urine was collected at weeks 2 and 6 for creatinine and decalol analyses and at week 12 for clinical urinalysis. Right kidneys were collected from male rats at weeks 2 and 6 and from both sexes at week 13, homogenates were prepared using the whole kidney, and these homogenates were analyzed for alpha2u-globulin, decalin, and 2-decalone. Left kidneys were evaluated for histopathology and cell proliferation utilizing a proliferating cell nuclear antigen technique and counting proximal renal tubular epithelial cells to determine cell labeling indices. Necropsies and histopathologic evaluations were performed at week 13. Decalin exposure caused increases in kidney weight, urinalysis parameters (protein, AST, LDH), kidney alpha2u-globulin concentration, and proximal convoluted renal tubular cell proliferation in males. These changes were accompanied by microscopic lesions (accumulation of hyaline droplets in cortical tubules, regeneration of proximal tubular epithelium, and granular casts in medullary tubules) clearly linked to alpha2u-globulin nephropathy. Both decalin and 2-decalone were related to increased alpha2u-globulin in male kidneys. Kidney concentrations of decalin, 2-decalone, and alpha2u-globulin in exposed females were negligible, while females excreted greater amounts of decalol metabolites in urine than males at weeks 2 and 6. There were no exposure-related microscopic lesions in females. For chronic exposure, F344 rats were exposed via whole-body inhalation to 0, 25, 50 (males only), 100, or 400 ppm decalin for two years. Chronic exposure induced a spectrum of nonneoplastic and neoplastic lesions in the renal cortex of males, ranging from regenerative lesions of chronic nephropathy to tubular carcinomas. Incidences of renal tubular adenoma, tubular carcinoma, combined tubular adenomas and carcinomas, cortical tubular hyperplasia, hyaline droplet accumulation, hyperplasia of pelvic epithelium, and mineralization in renal papilla were increased in exposed males compared to controls. There was a clear increase in the mean severity of chronic nephropathy in decalin-exposed males. It was concluded that the carcinogenic effect on the renal cortical epithelium of male rats exposed to decalin was related to increased turnover of this epithelium, resulting from the cytotoxic effects of alpha2u-globulin accumulation in the renal cortical tubular cell cytoplasm.     

Metabolism and nephrotoxicity of indan in male Fischer 344 rats

Indan, a component of fuels, solvents, and varnishes, is metabolized in male Fischer 344 rats to 1-indanol, 2-indanol, 5-indanol, 1-indanone, 2-indanone, 2-hydroxy-1-indanone, cis-1,2-indandiol, and trans-1,2-indandiol. The metabolites were identified using the techniques of gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The rats treated with indan demonstrated the classic lesions of hydrocarbon-induced nephropathy. The kidney damage produced was less than that found for tetralin and other branched-chain acyclic hydrocarbons.     

Percutaneous absorption of cis- and trans-permethrin in rhesus monkeys and rats: anatomic site and interspecies variation

Dermal absorption of cis- and trans-permethrin isomers was determined in rhesus monkeys and Sprague-Dawley rats. Four 14C radiolabels were used (cis alcohol, cis cyclopropyl, trans alcohol, and trans cyclopropyl). One microcurie of each radiolabel was applied to either the forehead or forearm of rhesus monkeys or to the midlumbosacral region of the rat. Urine was collected for 7 or 14 d. Correction factors for incomplete urine excretion were derived from measurements of radiolabel in the urine following im injection of an equivalent dose. It was noted that the total im dose recovered in the urine of both species was lower for the cis isomer than for the trans isomer. There was no significant difference between the dermal absorption of the cis isomer and that of the trans isomer in monkeys. The forehead, however, was more permeable for both isomers than the forearm (alcohol- and cyclopropyl-labeled cis and trans isomers, respectively, showed permeation in forehead, cis 28 +/- 6%, 24 +/- 6%, trans 21 +/- 3%, 14 +/- 4%, forearm, cis 9 +/- 3%, 9 +/- 3%, trans 12 +/- 3%, and 5 +/- 2%). There was no difference between absorption of the isomers (cis 46 +/- 4%, trans 43 +/- 5%) in rats, but absorption was significantly greater than in monkeys. The IM urinary t1/2 values in monkeys and rats were similar for both isomers (0.8-1.1 d).     

Protective Role of Metallothionein on DNA Damage in Rat Kidney Caused by Cis‐Diamminedichloroplatinum

Cis‐diamminedichloroplatinum (cis‐DDP) has been used as an anticancer agent but it also causes nephrotoxicity. To study the cis‐DDP metabolism and its effects, the induction of metallothioneins and DNA damage caused by cis‐DDP were observed. Cis‐DDP or trans‐DDP was administered to seven‐week‐old Wistar male rats as three daily injections of 8.0 mg/kg body wt., intraperitoneally. Using the obtained kidneys, gel filtration assay, metal analysis, immunohistochemistry and terminal deoxy transferase‐mediated deoxy uracil triphosphate nick end labeling (TUNEL) method were carried out to examine localization of metallothioneins and DNA damage caused by cis‐DDP. Platinum (Pt) contents, 26.05±12.01 μg/g body wt. and 51.29±4.59 μg/g body wt. (average±S.E.) were detected in the kidney of rats injected with both cis‐ and trans‐DDP, respectively. Metallothionein was detected in the cortex of the kidney in rats administrated cis‐DDP or trans‐DDP. The mRNA was also detected in the same region. On the other hand cis‐DDP showed induction of DNA damage on the cells in the outer stripe of the outer medulla but trans‐DDP did not show any damage. The region‐induced DNA damage differed from that induced by metallothioneins. Cis‐DDP is suggested to be mainly trapped at the proximal tubules by metallothioneins, and the rest of cis‐DDP induces DNA damage at the outer stripe of the outer medulla. Metallothioneins are considered to contribute to the protection against cis‐DDP in the rat cortex.     

Electrophysiological deficiency in peripheral nerve induced by treatment for 12 weeks with 2-butenenitrile, 3-butenenitrile, cis-2-pentenenitrile and 3,3-iminodipropionitrile in rats.

Motor and sensory conduction velocities and amplitudes of the sensory and motor action potentials of the tail nerve were studied in male Sprague-Dawley rats during subchronic oral treatment with three unsaturated aliphatic nitriles. The rats were given, by gastric intubation, doses of 10, 20 and 40 mg x kg(-1) 3-butenenitrile (allyl cyanide) and 25, 50 and 100 mg x kg(-1) of either cis/trans-2-butenenitrile (crotononitrile) or cis-2-pentenenitrile once a day, 5 days per week for 12 weeks. Moreover, 3,3'-iminodipropionitrile was administered likewise at doses of 25, 50 and 100 mg x kg(-1) as reference neurotoxicant. Oral administration of the three unsaturated nitriles produced deafness and absence of reaction when the animals were subject to droptest. Moreover, rats exhibited both time- and concentration-dependent decreases in motor and sensory conduction velocities and amplitudes of the sensory action potentials. Nerve conduction velocities were partially reversible after 8 weeks of recovery. Rats receiving 3,3'-iminodipropionitrile developed deafness, head weaving and significant irreversive deficiencies in all the electrophysiological parameters studied. Further toxicological studies with related unsaturated nitriles should be carried out to determine the potential importance of the cis/trans isomerism in the observed neurotoxicity.     

Antibacterial and antifungal agents. XV. Synthesis and antifungal activity of structural analogues of bifonazole and ketoconazole.

The synthesis and antifungal activities of the cis- and trans-1-acetyl-4-[4-[[2-(1,1'-biphenyl-4-yl)-2-(1H-imidazol-1-ylmethy l)- 1,3-dioxolan-4-yl]-methoxy]phenyl)piperazines 3 and 4 are reported. Stereochemical assignments to diastereomeric pairs of cis/trans isomers were made on the basis of 1H- and 13C-NMR data. Among test derivatives the best activity was shown by the benzoyl esters of the cis- and trans-[2-(1,1'-biphenyl-4-yl)-2-(1H-imidazol-1-ylmethyl)-1,3-di oxolan-4- yl]methanols 9 and 10.     

Reversion of structure-activity relationships of antitumor platinum complexes by acetoxime but not hydroxylamine ligands

The presence of cis-configured exchangeable ligands has long been considered a prerequisite for antitumor activity of platinum complexes, but over the past few years, several examples violating this structure-activity relationship have been recognized. We report here on studies with the geometric isomers of [PtCl2(acetoxime)2], cis-[dichlorobis(acetoxime)platinum(II)] [1 (cis)] and trans-[dichlorobis(acetoxime)platinum(II)] [2 (trans)], as well as those of [PtCl2(hydroxylamine)2], cis-[dichlorobis(hydroxylamine)platinum(II)] [3 (cis)] and trans-[dichlorobis(hydroxylamine)platinum(II)] [4 (trans)]. We found that 2 (trans)is 16 times more cytotoxic than 1 (cis) and as cytotoxic as cisplatin in cisplatin-sensitive ovarian carcinoma cells (CH1). Moreover, 2 (trans) is 15 times more cytotoxic than either cisplatin or 1 (cis) in intrinsically cisplatin-resistant colon carcinoma cells (SW480). Thus, compound 2 (trans) represents a novel type of active platinum(II) complexes of the trans geometry, whereas the hydroxylamine-containing complexes conform to the classic structure-activity relationships. The reactivity of the compounds toward dGMP and DNA and their capacity to alter the structure of double-stranded DNA and form interstrand cross-links were studied by capillary electrophoresis and gel electrophoresis. The slow binding of 2 (trans) to dGMP (tau(1/2) = 50 h versus 8.9 h in the case of cisplatin), the low reactivity toward DNA, the comparatively small impact on DNA secondary structure, and the lack of detectable interstrand cross-linking suggest a mode of action fundamentally different from that of cisplatin. Implications of our findings for the minimal structural requirements (e.g., planarity around the nitrogen donor atom and/or ramified aliphatic moiety attached to the latter) of active trans-configured platinum complexes are discussed.     

Comparison of local anesthetic activities between cis and trans isomers of DL-1-benzoyloxy-2-dimethylamino-1,2,3,4-tetrahydronaphthalene.

The local anesthetic activities of cis- and trans- dl-1-benzoyloxy-2-dimethylamino-1,2,3,4-tetrahydronaphthalene were compared using several methods with guinea-pigs. The cis compound (YAU-17) was 2.9 to 6 times as potent as its trans isomer and exceeded procaine, lidocaine and cocaine in potencies of corneal anesthesia, intracutaneous anesthesia and sciatic nerve block. In another experiment on isolated frog sartorius muscle, all of the local anesthetics suppressed the twitch contractions elicited by stimulation of the sciatic nerve. The neuromuscular blocking activity of the cis compound was more pronounced than that of the trans form. Supersensitivity to noradrenaline was produced by both of the stereoisomers in isolated vas deferens of guinea-pigs although there was no difference in the activity. The sensitizing action was also demonstrable with cocaine and lidocaine but not with procaine. When injected intravenously into mice, the cis compound was twice as toxic as its isomer. It is postulated that stereoselectivity is to some extent involved in the mechanisms of action of the local anesthetic agents.     

Electrophysiological Deficiency in Peripheral Nerve Induced by Treatment for 12 Weeks with 2-Butenenitrile, 3-Butenenitrile,cis-2-Pentenenitrile and 3, 3′-Iminodipropionitrile in Rats

Abstract: Motor and sensory conduction velocities and amplitudes of the sensory and motor action potentials of the tail nerve were studied in male Sprague-Dawley rats during subchronic oral treatment with three unsaturated aliphatic nitriles. The rats were given, by gastric intubation, doses of 10, 20 and 40 mg × kg^–1 3-butenenitrile (allyl cyanide) and 25, 50 and 100 mg × kg^–1 of either cis/trans-2-butenenitrile (crotononitrile) or cis-2-pentenenitrile once a day, 5 days per week for 12 weeks. Moreover, 3, 3′-iminodipropionitrile was administered likewise at doses of 25, 50 and 100 mg × kg^–1 as reference neurotoxicant. Oral administration of the three unsaturated nitriles produced deafness and absence of reaction when the animals were subject to droptest. Moreover, rats exhibited both time- and concentration-dependent decreases in motor and sensory conduction velocities and amplitudes of the sensory action potentials. Nerve conduction velocities were partially reversible after 8 weeks of recovery. Rats receiving 3, 3′-iminodipropionitrile developed deafness, head weaving and significant irreversive deficiencies in all the electrophysiological parameters studied. Further toxicological studies with related unsaturated nitriles should be carried out to determine the potential importance of the cis/trans isomerism in the observed neurotoxicity.     

Synthesis and carcinogenic activity of 5-fluoro-7-(oxygenated methyl)-12-methylvenz[a]anthracenes.

Treatment of 7,12-benz[a]anthraquinone (2) with methylmagnesium iodide or methyllithium yields mixtures of cis- and trans-7,12-dihydro-7,12-dihydroxy-7,12-dimethylbenz[a]anthracenes (3a,b), in which the ratio of cis to trans lies in the 3--4:1 region. Each isomer afforded high yields of 7-chloromethyl-12-methylbenz[a]anthracene (5) on treatment with hydrogen chloride in ethyl acetate. Similarly, 5-fluoro-7,12-benz[a]anthraquinone (8) afforded a mixture of cis- and trans-5-fluoro-7,12-dihydro-7,12-dihydroxy-7,12-dimethylbenz[a]anthracenes (9) which yielded 7-chloromethyl-5-fluoro-12-methylbenz[a]anthracene (10) on treatment with HCl. The chloromethyl compounds, 5 and 10, yielded 7-acetoxymethyl-12-methylbenz[a]anthracene (6) and 7-acetoxymethyl-5-fluoro-12-methylbenz[a]anthracene (11) on treatment with acetate ion. Hydrolysis of 6 and 11 yielded 7-hydroxymethyl-12-methylbenz[a]anthracene (7) and 5-fluoro-7-hydroxymethyl-12-methylbenz[a]anthracene (12), respectively. Since neither 11 nor 12 is appreciably carcinogenic, the carcinogenic metabolism of 7,12-dimethylbenz[a]anthracene (DMBA) probably does not involve attack at the 7-methyl group.     

Conformationally restricted analogs of histamine H1 receptor antagonists: trans and cis-1-benzyl-3-dimethylamino-6-phenylpiperidine.

The syntheses of trans- and cis-1-benzyl-3-dimethylamino-6-phenylpiperidine (1 and 2) are described. Compounds 1 and 2 were found to be inhibitors to histamine, acetylcholine, and barium chloride induced contractions of the isolated guinea pig ileum. Compounds 1 and 2 do not exhibit appreciable stereoselectivity in their ability to inhibit smooth muscle contractions. The cis compound 2 is a more effective inhibitor of histamine N-methyltransferase than the trans isomer 1.     

Actinonin, a meprin inhibitor, protects ischemic acute kidney injury in male but not in female rats

We investigated the effects of actinonin, an inhibitor of a matrix-degrading enzyme meprin, on ischemic acute kidney injury in male and female rats, and these were compared with the effects of verapamil, a Ca(2+) channel blocker. Ischemic acute kidney injury was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. At 24 h after reperfusion, renal function and histology of both males and females showed significant deterioration. The degrees of renal dysfunction and histological damage were much more severe in males than in females. Pre-ischemic treatment with actinonin (10 or 30 mg/kg, i.v.) dose-dependently attenuated the ischemia/reperfusion-induced renal injury in male rats, but failed to improve the renal injury in female rats. On the other hand, verapamil (1 mg/kg, i.v.) could efficiently prevent the ischemic acute kidney injury in female rats, as well as male rats. These results indicate that the renoprotective effect of actinonin is male-specific, thereby suggesting that meprin is involved in exacerbation of ischemia/reperfusion-induced renal injury in male rats. The possibility that meprin is a key factor involved in the sex difference in the pathogenesis of ischemic acute kidney injury, warrants further attention.     

Synthesis and in vitro antitumor activity of platinum acetonimine complexes

The cis- and trans-dichloro- and diiodo-platinum(II) complexes containing two acetonimines (cis- and trans-[PtX(2){HN=C(CH(3))(2)}(2)], 1 and 2 for X = Cl and 1' and 2' for X = I, respectively) or one acetonimine and one ammine (cis- and trans-[PtX(2)(NH(3)){HN=C(CH(3))(2)}], 3 and 4 for X = Cl and 3' and 4' for X = I, respectively) have been prepared from platinum-ammine precursors by condensation with acetone. Except for the cis-diiodo species, in all other cases the presence of a base was required. A crucial role of the ligand trans to the ammine undergoing condensation with acetone has been disclosed: the greater the trans effect the greater the reactivity. In a panel of human tumor cell lines representative of ovarian, colon, lung, and breast cancers, cis complexes 1 and 3 are less active than cis-DDP (mean IC(50) = 20, 12.5, and 2.8 microM, respectively), whereas trans complexes 2 and 4 are more active than trans-DDP (mean IC(50) = 10.6, 26, and 164 microM, respectively), thus indicating that substitution of acetonimine for one or two ammine ligands determines strikingly different effects depending upon the complex geometry.     

The ototoxic effects induced in rats by treatment for 12 weeks with 2-butenenitrile, 3-butenenitrile and cis-2-pentenenitrile

Brainstem auditory and visual evoked-potentials were studied in male Sprague-Dawley rats during subchronic oral treatment with three unsaturated aliphatic nitriles. The rats were given, by gastric intubation, doses of 10, 20 and 40 mg x kg(-1) 3-butenenitrile (allyl cyanide) and 25, 50 and 100 mg x kg(-1) of either cis/trans-2-butenenitrile (crotononitrile) or cis-2-pentenenitrile once a day, 5 days per week for 12 weeks. Oral administration of the three unsaturated nitriles produced deafness and absence of reaction when the animals were subject to droptest. Rats in the high dosage groups exhibited a complete disappearance of the five waves of the auditory evoked-potentials. There was a decrease in the amplitudes of the 2nd component of the auditory evoked-potentials. Those changes were not reversible at the 8th week of the recovery period. A dose-dependent effect on inner and outer hair cells was observed in the organ of Corti. The basal part of the cochlea was the most affected. Though no measurements were made of systemic exposure, a tentative ranking of decreasing ototoxicity of these three unsaturated nitriles might be proposed based on the electrophysiological deficiencies and histological losses observed: 3-butenenitrile >cis-2-pentenenitrile >cis/trans-2-butenenitrile. Moreover, rats treated with those nitriles showed a corneal opacity as well as a decrease in the amplitude and lengthening of the peak latencies of the visual evoked-potentials. These latter changes were reversible by the end of the 8th week of the recovery period and appeared to be related to the opacity of the cornea.     

trans-N-n-Propyl-7-hydroxy-octahydrobenzo(f)quinoline, a rigid 3-PPP analogue with greater potency but lack of selectivity for dopamine autoreceptors

trans- and cis-7-hydroxy-octahydrobenzo(f)quinoline were synthesized as analogues of the selective dopamine autoreceptor agonist 3-PPP. The trans compound appeared more effective than 3-PPP in the dopamine autoreceptor test model, but it also exhibited postsynaptic dopamine receptor stimulating activity. The cis compound was inactive in both these test models. It is concluded that in the trans compound the dopamine autoreceptor stimulating potency of 3-PPP has been much enhanced at the cost of dopamine autoreceptor selectivity.