Mechanism of chloroform nephrotoxicity : II. In vitro evidence for renal metabolism of chloroform in mice

Preincubation of renal cortical slices with chloroform (CHCl₃) from male, but not female, mice resulted in a subsequent decrease of the ability of the slices to accumulate the organic ions, p-aminohippurate (PAH) and tetraethylammonium (TEA). These sex-related differences, the time required for manifestation of this effect (60 to 90 min), and the concentration dependency (0 to 50 μmol, 0 to 4 μl CHCl₃) were similar to in vivo observations on CHCl₃ nephrotoxicity in mice. Furthermore, an equimolar concentration of deuterated CHCl₃ (CDCl₃) in vitro was less effective than CHCl₃ in decreasing PAH and TEA accumulation in male renal cortical slices. The effects of CHCl₃ on PAH and TEA accumulation could be diminished or blocked by preincubation with CHCl₃ in the presence of carbon monoxide or at 0°C, respectively. The nephrotoxicity of CHCl₃ in vitro was increased in renal cortical slices from male mice pretreated with diethyl maleate. Thus, this in vitro model with mouse renal cortical slices and the sex-related differences in CHCl₃ nephrotoxicity suggests that the kidney may metabolize CHCl₃ in situ to a nephrotoxic metabolite.     

Mechanism of chloroform nephrotoxicity. III. Renal and hepatic microsomal metabolism of chloroform in mice

In vitro studies with male ICR mouse renal cortical slices have indicated that chloroform (CHCl3) is metabolized by the kidney to a nephrotoxic intermediate, possibly by a cytochrome P-450-dependent mechanism similar to that occurring in the liver. In this investigation, metabolism of 14CHCl3 by microsomes prepared from renal cortex and liver provided definitive evidence for a role of cytochrome P-450 in the renal metabolism and toxicity of CHCl3. 14CHCl3 was metabolized to 14CO2 and covalently bound radioactivity by male renal cortical microsomes; metabolism required oxygen, a NADPH regenerating system, was dependent on incubation time, microsomal protein concentration, and substrate concentration, and was inhibited by carbon monoxide. Consistent with the absence of CHCl3 nephrotoxicity in female mice, little or no metabolism of 14CHCl3 by female renal cortical microsomes was detected. CHCl3 produced a type I binding spectrum with oxidized male renal cortical and hepatic microsomes. Incubation of glutathione with microsomes and 14CHCl3 increased the amount of aqueous soluble metabolites detected with a concomitant decrease of metabolism to 14CO2 and covalently bound radioactivity, suggesting the formation of a phosgene conjugate as has been described for hepatic CHCl3 metabolism. These data support the hypothesis that renal cytochrome P-450 metabolizes CHCl3 to a nephrotoxic intermediate.     

Mechanism of chloroform nephrotoxicity: IV. Phenobarbital potentiation of in vitro chloroform metabolism and toxicity in rabbit kidneys

Metabolism of chloroform (CHCl₃) by a cytochrome P-450-dependent process to a reactive metabolite may be required to elicit hepatic and renal toxicities. Specific inducers or inhibitors of cytochrome P-450 have been employed frequently as tools to demonstrate this relationship between metabolism and toxicity in the liver. The experiments reported herein were designed to identify the relationship between metabolism and toxicity of CHCl₃ in the kidney of rabbits, a species in which renal cytochrome P-450 is induced by phenobarbital. Pretreatment with phenobarbital enhanced the toxic response of renal cortical slices to CHCl₃in vitro as indicated by decreased p-aminohippurate and tetraethylammonium accumulation. Phenobarbital pretreatment also potentiated in vitro¹⁴CHCl₃ metabolism to ¹⁴CO₂ and covalently bound radioactivity in rabbit renal cortical slices and microsomes. Addition of l-cysteine significantly reduced covalent binding in renal microsomes from both phenobarbital-treated and control rabbits and was associated with the formation of the radioactive phosgene-cysteine conjugate 2-oxothiazolidine-4-carboxylic acid (OTZ). Formation of OTZ was enhanced in renal microsomes from phenobarbital-pretreated rabbits. Thus, this in vitro model supports the hypothesis that the kidney metabolizes CHCl₃ to the nephrotoxic metabolite, phosgene.     

Influence of dietary pectin on intestinal microfloral metabolism and toxicity of nitrobenzene

Intestinal microfloral metabolism of nitrobenzene is essential for the production of methemoglobin. Since dietary pectin alters intestinal microflora, these studies were designed to examine the effects of dietary pectin on nitrobenzene-induced methemoglobinemia. Male Fischer-344 rats were fed either AIN-76A (purified diet containing 5% cellulose), AIN-76A with 5% pectin replacing the cellulose, or NIH-07 (cereal-based diet containing 8.4% pectin) for 28 days. Following this period, nitrobenzene (200 mg/kg) was administered by gastric intubation, and methemoglobin concentrations were determined after 1, 2, 4, 8, and 24 hr. Nitrobenzene-induced methemoglobinemia was evident as early as 1 hr, peaked at 4 hr, and diminished thereafter in rats fed NIH-07 diet. In contrast, nitrobenzene-induced methemoglobinemia was not detectable in rats fed AIN-76A; however, inclusion of 5% pectin in this diet resulted in methemoglobinemia comparable to that of NIH-07-fed animals at 4, 8, and 24 hr. Administration of 400 or 600 mg/kg nitrobenzene resulted in significant diet-related differences in methemoglobinemia. Administration of 600 mg/kg nitrobenzene to animals fed NIH-07 resulted in the highest methemoglobin concentrations (64 ± 1%); those fed AIN-76A had the lowest (20 ± 5%), and those fed AIN-76A containing pectin had intermediate methemoglobin concentrations (44 ± 6%). No diet-related differences in the microbial population of the stomach or small intestine were observed. However, the number of anaerobes present in the ceca of rats fed AIN-76A containing pectin was 2 to 2.5 times greater than that of rats fed AIN-76A. In vitro reductive metabolism of [¹⁴C]nitrobenzene was significantly greater in the cecal contents of rats fed NIH-07 than that in the cecal contents of either of the groups fed the AIN-76A-based diets. These studies indicate that intestinal microfloral metabolism and red blood cell toxicity of nitrobenzene is markedly different in animals fed cereal-based versus purified diets. Furthermore, since inclusion of pectin into the purified diet diminishes the magnitude of these effects, differences in dietary composition of fermentable carbohydrates in cereal-based and purified diets may mediate differences in metabolism and toxicity of nitrobenzene.     

Differential toxicity of trans-permethrin in rainbow trout and mice: I. Role of biotransformation

The trans isomer of [1R,S] permethrin (t-per) was > 110 times more toxic to rainbow trout than to mice by both iv and ip administration. The importance of trans-permethrin biotransformation in this differential toxicity was assessed by measuring rates of t-per biotransformation in trout and mouse tissues in vitro, and the effect of inhibitors of drug metabolism on t-per lethality in both species. A previous study had shown that ester hydrolysis by trout liver, plasma, and kidney is much slower than that seen in these same tissues in mice. The present work further indicates that oxidation of t-per is 35 times slower in trout liver microsomes than mouse microsomes when the tissue suspensions were incubated at the body temperature of trout and mice (12°C for trout and 37°C for mice). Inhibition of esterase activity with tri-o-tolyl phosphate (TOTP) produced no potentiation of t-per lethality in trout while the same compound potentiated t-per lethality at least 1.5-fold in mice. Piperonyl butoxide (PIP) alone produced no potentiation in mice but slightly increased t-per toxicity when administered in conjunction with TOTP. PIP caused a slight increase in t-per lethality in rainbow trout but no increase in t-per lethality from control was observed when trout were pretreated with both TOTP and PIP. When drug metabolism was inhibited, t-per was still 65 times more toxic to trout than to mice. The data indicate that trout, in addition to hydrolyzing t-per slowly, also oxidize the compound considerably slower than mice in vitro. Potentiation of t-per lethality by TOTP suggests ester hydrolysis to be an important t-per detoxification reaction in mice but not in trout. However, since t-per was 65 times more toxic to the trout than mouse when drug metabolism was inhibited, other factors, such as differences in target organ sensitivity may be involved in the differential toxicity of permethrin.     

Identification and quantification of urinary metabolites of dinitrotoluenes in occupationally exposed humans

Rats exposed to technical grade dinitrotoluene (DNT) develop hepatocellular carcinomas. Humans may be exposed to DNT during its manufacture and use. To permit comparisons of human excretion patterns of DNT metabolites with those previously observed in rats, urine specimens were collected over a 72-hr period from workers at a DNT manufacturing plant. Samples were analyzed for 2,4- and 2,6-DNT and putative metabolites by gas chromatography-mass spectrometry. Urine from workers exposed to DNT contained 2,4- and 2,6-DNT, 2,4- and 2,6-dinitrobenzoic acid, 2,4- and 2,6-dinitrobenzyl glucuronide, 2-amino-4-nitrobenzoic acid, and 2-(N-acetyl)amino-4-nitrobenzoic acid. Excretion of these metabolites peaked near the end of the workshift, but declined to either very low or undetectable concentrations by the start of work the following day. The calculated half-times for elimination of total DNT-related material detected in urine ranged from 1.0 to 2.7 hr, and those of individual metabolites from 0.8 to 4.5 hr. The most abundant metabolites were 2,4-dinitrobenzoic acid and 2-amino-4-nitrobenzoic acid, collectively accounting for 74 to 86% of the DNT metabolites detected. The data indicate that urinary metabolites of DNT in humans are qualitatively similar to those found in rats, but quantitative differences exist in the relative amounts of each metabolite excreted.     

The chronic toxicity of technical and analytical pentachlorophenol in cattle. I. Clinicopathology

The objectives of this study in female yearling Holstein cattle were to define the toxic effects of (1) long-term exposure to analytical pentachlorophenol (aPCP), and (2) to determine the influence of the contaminants in technical pentachlorophenol (tPCP) in the toxic syndrome. Four groups of three heifers each were exposed for 160 days to aPCP, tPCP, or a mixture thereof in the feed. A fifth group of three animals served as unexposed controls. All treated cattle received the same amount of PCP; 20 mg/kg/day for 42 days which was reduced to 15 mg/kg/day for the remainder of the study because of a suspected decrease in body weight gain in all PCP-exposed animals compared to controls. Fat and liver samples for chemical analyses were collected at the end of the study. Major findings in the tPCP-exposed heifers included a dose-related decrease in body weight, decreased feed efficiency, progressive anemia, a dose-related increase in liver and lung weights, and a decrease in thymus weight. The most conspicuous lesion was market villous hyperplasia of the urinary bladder mucosa in two of three animals exposed to the highest level of tPCP. There were minimal hepatic lesions although hyperplasia of the mucosal lining of the gali bladder and bile duct was noted in some animals exposed to tPCP. Animals exposed to aPCP were, in general, comparable to the controls. Hepatic mixed function oxidases were increased by aPCP, but more so by tPCP. A decrease in thyroxine concentration was found in all PCP-treated cattle. Immunologic studies suggested a progressive tPCP dose-related enhancement in the lymphoproliferative response, an in vitro correlate for cell-mediated immunity. Observed effects on humoral immune parameters were equivocal. The results of this study indicate that toxicity of PCP in cattle is primarily attributable to its contamination with toxic impurities.     

Differential toxicity of trans-permethrin in rainbow trout and mice: II. Role of target organ sensitivity

Previous studies demonstrated that even when trans-permethrin ester hydrolysis was inhibited in mice and the toxicity of trans-permethrin was increased at least 1.6 times by tri-o-tolyl phosphate (TOTP), the toxicity of trans-permethrin remained 60 times greater in the rainbow trout than in the mouse. This information suggested that factors other than metabolism, such as target organ sensitivity, may play a role in the differential toxicity of trans-permethrin between rainbow trout and mice. Since the brain of both the fish and the mouse is believed to be a site of action of the pyrethroids, the concentration of permethrin in the brains of these two species at the onset of signs of pyrethroid toxicity was measured in an attempt to establish a correlation between permethrin brain levels and toxicity in the fish and mammal. Signs of pyrethroid toxicity, such as intense whole body twitches and loss of equilibrium, were observed in rainbow trout when ¹⁴C-trans-permethrin brain levels exceeded 1.5 μg/g brain, regardless of whether the compound was administered iv or ip. Pyrethroid toxicity signs, such as intense tremors and loss of righting, were not observed in mice until ¹⁴C-trans-permethrin levels reached 25 to 30 μg/g brain. Thin-layer chromatographic analysis indicated that 85 to 95% of the ¹⁴C was parent compound in the rainbow trout brains compared to 60 to 70% in the mouse brains. ¹⁴C-cis-Permethrin produced lethality in trout and mice when the ¹⁴C-cis-permethrin brain concentrations were 2 and 6 μg/g, respectively. The results suggest that the rainbow trout may be physiologically more sensitive to the action of permethrin than is the mouse. In the trout, the cis and trans isomers appear to be equal in toxicity while in the mouse the cis isomer is more active than the trans isomer. The difference in isomer sensitivity between the trout and mouse may suggest differences in specificities at the site of pyrethroid action. The physiologic basis for this difference in pyrethroid toxicity is not understood.     

Species differences in response to trichloroethylene. I. Pharmacokinetics in rats and mice

The elimination of radioactivity in two strains of rats and mice following a single po dose of trichloro[14C]ethylene at dose levels from 10 to 2000 mg/kg has shown a marked dose dependence in rats but not in mice. The metabolism of trichloroethylene in the mouse was linear over the range of doses used, whereas in the rat it became constant and independent of dose at 1000 mg/kg and above. At the 10-mg/kg dosage, both species metabolized trichloroethylene almost completely, 60% of the dose being excreted in urine with only 1 to 4% being eliminated unchanged in expired air in the first 24 hr. At 2000 mg/kg, 78% of the dose was eliminated unchanged in the rat, but only 14% in the mouse. Consequently at high dosages, the mouse was exposed to significantly higher concentrations of trichloroethylene metabolites than the rat. Blood level kinetics of trichloroethylene and its metabolites confirmed a faster rate of metabolism in the mouse than in the rat. Peak concentrations of the metabolites were reached within 2 hr of dosing in the mouse compared to 10 to 12 hr in the rat. The concentrations of both trichloroethanol (4X) and trichloroacetic acid (7X) were significantly higher in the mouse than in the rat. Whereas trichloroethanol was rapidly eliminated from blood, the higher concentrations of trichloroacetic acid were maintained for over 30 hr. The high blood quantities of trichloroethylene-derived trichloroacetic acid are known to induce hepatic peroxisome proliferation in mice but are insufficient to induce this response in rats. These data suggest that trichloroacetic acid blood amounts, peroxisome proliferation, and the link between peroxisomes and liver cancer are the basis of species difference in response to trichloroethylene.     

The metabolism and disposition of hexachloro-1:3-butadiene in the rat and its relevance to nephrotoxicity

Following po administration of a nephrotoxic dose (200 mg/kg) of hexachloro-1:3-butadiene (HCBD) to male rats, the principal route of excretion was biliary, 17-20% of the dose being eliminated on each of the first 2 days. Fecal excretion over this period was less than 5% of the dose per day, suggesting enterohepatic recirculation of biliary metabolites. Urinary excretion was small, not exceeding 3.5% of the dose during any 24-hr period. The major biliary metabolite was a direct conjugate between glutathione and HCBD itself. The cysteinylglycine conjugate of HCBD has also been found in bile. Evidence was obtained to show that biliary metabolites of HCBD are reabsorbed and excreted via the kidneys. The glutathione conjugate, its mercapturic acid derivative, and bile containing HCBD metabolites were all nephrotoxic when dosed orally to rats. In common with HCBD, these metabolites caused localized damage to the kidney with minimal effects in the liver. Rats fitted with a biliary cannula were completely protected from kidney damage when dosed with HCBD, demonstrating that hepatic metabolites were solely responsible for the nephrotoxicity of this compound. It is proposed that the hepatic glutathione conjugate of HCBD was degraded to its equivalent cysteine conjugate which was cleaved by the renal cytosolic enzyme beta-lyase to give a toxic thiol which caused localized kidney damage. A urinary sulphenic acid metabolite of HCBD has been identified which is consistent with this hypothesis. The mode of activation of HCBD conjugates in the kidney is believed to be analogous to that proposed for S-(1,2-dichlorovinyl)-L-cysteine.     

Species differences in response to trichloroethylene. II. Biotransformation in rats and mice

Detailed analysis of urine from two strains of rats and mice dosed po with trichloroethylene at four doses from 10 to 2000 mg/kg failed to detect any major species or strain differences in the metabolism of trichloroethylene. Although a greater proportion of the dose was metabolized in mice than in rats, the relative proportions of the major metabolites were very similar in both strains and were unaffected by the dose amount. Analysis of the same urine samples for minor metabolites failed to establish a major species difference. Small amounts of dichloroacetic acid (less than 1% of the dose) were present in both rat and mouse urine and were not considered significant. Monochloroacetic acid accounted for less than 0.1% of the dose. Daily dosing of trichloroethylene (1000 mg/kg po) for 180 days did not induce the overall metabolism of trichloroethylene but did double the urinary excretion of trichloroacetic acid. This finding was accompanied by an equivalent percentage decrease in the concentration of trichloroethanol. CO2 has been shown to be a major metabolite of trichloroacetic acid, suggesting that this is the source of trichloroethylene-derived CO2. Trichloroacetic acid was also excreted in bile in both rats and mice suggesting possible conjugation of this metabolite in the liver. Very little evidence was found for the formation of chemically reactive species from trichloroethylene in either rats or mice and none that could be the basis of a major species difference. The increased rate of metabolism in the mouse, the resulting high blood concentrations of trichloroacetic acid, and stimulation of hepatic peroxisome proliferation in this species appears to be the major species difference possibly related to tumor formation in the liver. The conjugation of trichloroacetic acid and its metabolism to CO2 may be related to peroxisome proliferation.     

Gastrointestinal absorption of cadmium in mice during gestation and lactation: II. Continuous exposure studies

The effect on cadmium retention of continuous exposure to drinking water containing low levels of cadmium during pregnancy and lactation was studied in mice. Female mice were provided drinking water ad libitum containing ¹⁰⁹CdCl₂ (0.03 μCi ¹⁰⁹Cd/ml, 0.11 ppb total cadmium) throughout either gestation, lactation, or a combined period of pregnancy and lactation. Nonpregnant control mice were exposed to the same cadmium solution for similar time periods. Dams in all three experimental groups retained two to three times more cadmium (expressed as percentage of ingested dose) than did nonpregnant controls. The ¹⁰⁹Cd contents of liver, kidney, mammary tissue, and duodenum increased strikingly in all three groups. Increases in kidney and mammary tissue were particularly apparent during lactation, with increases of fivefold for kidney and at least ninefold for mammary tissue, compared to levels in nonpregnant controls. Increases in ¹⁰⁹Cd retention by the duodenum were fivefold during gestation and three- to fourfold during lactation. The kidneys of dams exposed during lactation retained 53% of the whole body ¹⁰⁹Cd, while kidneys of nonpregnant controls retained only 27%. Results indicate that pregnant and lactating mice absorb and subsequently retain substantially more cadmium from their diets than do nonpregnant mice.     

The toxicity of some N-methyl-N-formylhydrazones from Gyromitra esculenta and related compounds in mouse and microbial tests.

The acute oral toxicity of four N-methyl-N-formylhydrazones (compounds found in the edible mushroom Gyromitra esculenta Fr. ex Pers.), one N-methylhydrazone derivative and N-methyl-N-formylhydrazine, N-methylhydrazine, and hydrazine were compared in mice. The bacteriocidal effect of the last three compounds was also studied using Escherichia coli as a test organism. N-Methylhydrazine and N-methyl-N-formylhydrazine were both found to be considerably more toxic to mice than N-methyl-N-formylhydrazones or hydrazine. Both hydrazine and N-methylhydrazine were clearly bacteriocidal to Escherichia coli, whereas N-methyl-N-formylhydrazine had no effect on the test bacterium at the doses used. The results are compatible with the hypothesis that the metabolic products of N-methyl-N-formylhydrazones, possibly N-methylhydrazine, are responsible for the toxic effects of these compounds.     

Effects of a polybrominated biphenyl mixture in the rat and mouse. I. Six-month exposure

A 1973 environmental accident in Michigan resulted in exposure of humans via the food chain to polybrominated biphenyl (PBB). To better characterize the toxicity of the halogenated polycyclic aromatic hydrocarbon class of chemicals, rodents were dosed with PBB and their target organs examined for morphological, histological, biochemical, and selected endocrine changes. Male and female rats and mice were given 125 po doses of PBB over a 6-month period at 0.1, 0.3, 1.0, 3.0, and 10.0 mg/kg of body weight/day (5 days/week). There was a dose-related decrease in body weight gain in both male and female rats and male mice. Thymus weights were significantly decreased in all rats exposed to 0.3 mg/kg or more of PBB. Dose-related hepatotoxic effects were observed in both rats and mice characterized by marked increase in liver weight with accentuation of hepatic lobular markings. Microscopically, there were moderate to marked swelling, disorganization, and single cell necrosis of hepatocytes, fatty infiltration, bile duct proliferation, and presence of atypical hyperplastic foci. Hepatic porphyrin levels were markedly increased in both rats and mice primarily in females. There was a significant decrease in serum thyroxine (T4) and triiodothyronine (T3) suggesting that PBB may interfere with thyroid hormone secretion. There was a significant dose-related increase in serum cholesterol and gamma-glutamyl transpeptidase, and a decrease in serum glucose.     

Hepatotoxicity and pulmonary toxicity of pennyroyal oil and its constituent terpenes in the mouse

Pennyroyal oil, an aromatic mint-like oil used as a flavoring and fragrance agent and as a herbal medicine, caused acute hepatic and lung damage at doses of 400 mg/kg, ip, and higher in male Swiss-Webster mice. Cellular necrosis was localized to the centrilobular regions of the liver and bronchiolar epithelial cells of the lung. Capillary gas chromatographic analysis of samples of pennyroyal oil that were obtained from health food stores showed the presence of several monoterpene constituents. R-(+)-Pulegone was the major terpene and constituted greater than 80% of the constituent terpenes in the oils that were examined. Pulegone and two other constituent terpenes, isopulegone and menthofuran, were found to be both hepatotoxic and lung toxic. Based on results of histologic scoring of necrosis, plasma GPT elevations, and hepatic glutathione depletion, R-(+)-pulegone is the terpene primarily responsible for the tissue necrosis. Furthermore, results of toxicity tests with several congeners of R-(+)-pulegone, including the enantiomeric S-(?)-pulegone, strongly implicated the α-isopropylidene ketone group as the structural unit required for eliciting hepatotoxicity, although the configurational orientation of the methyl group can modulate the hepatotoxic response.     

Ethyl acrylate-induced gastric toxicity. I. Effect of single and repetitive dosing

Ethyl acrylate (EtAc) is widely used in the production of polymers and copolymers for use in the preparation of latex paints, textiles, paper coatings, and specialty plastics. EtAc caused squamous cell carcinomas and papillomas in the forestomach (nonglandular portion of the stomach) of both sexes of F344 rats and B6C3F1 mice when administered chronically by gavage. The current studies were undertaken to investigate and characterize the nature of the acute gastric toxicity caused by EtAc. Gavage administration of a single dose of 100, 200, or 400 mg/kg EtAc (in corn oil) to F344 male rats caused dose-and time-dependent mucosal and submucosal edema and vacuolization of the tunica muscularis in the forestomach and mild submucosal edema in the glandular stomach. Equivalent sc or ip doses did not produce similar gastric lesions. Treatment of rats with two or four consecutive oral daily doses (200 mg/kg each) of EtAc caused mucosal edema associated with vesicle formation, mucosal hyperplasia, submucosal edema and inflammation, and vacuolization of the tunica muscularis of the forestomach. Submucosal edema and inflammation were also observed in the glandular stomach and mucosal erosions or ulcers were observed in both portions of the stomach after repeated oral exposure to EtAc. The absence of systemic toxicity plus the dependency of gastric lesions on the gavage route of administration suggest that the EtAc-induced gastric lesions may be a consequence of localized hemodynamic changes, specifically those characteristic of a classical immediate inflammatory response to an injurious agent at the site of administration.     

Effect of cadmium on plasma aldosterone and serum corticosterone concentrations in male rats

Cadmium chloride (CdCl2) at a dose of 1 mg/kg of body weight was injected into male Wistar rats twice a day (12-hr intervals) for 7 consecutive days. A group of treated rats was maintained without any treatment for an additional period of 10 days and killed on the following day (on Day 18). Plasma aldosterone concentrations were markedly increased in Cd-treated rats on Days 2, 3, and 8. The metabolic clearance rate (MCR) of plasma aldosterone on Day 3 was within the same range as the control value, and the production rate (PR) of aldosterone markedly increased on Day 3, suggesting that the increased plasma aldosterone on Day 3 may be associated with the increase of PR of aldosterone. The serum corticosterone concentration was significantly decreased on Day 8 while the MCR of corticosterone markedly increased on Days 3 and 8 and the PR of corticosterone also significantly increased on Days 3 and 8. The increased ratio (the value in treated rats/the value in control rats) in MCR of corticosterone on Day 8 was higher than that in PR of corticosterone on Day 8, suggesting that the increased MCR was a factor for the decreased serum corticosterone on Day 8. Serum potassium and sodium concentrations significantly increased on Days 1 and 3. No significant differences in Cd contents were observed between the zona glomerulosa and zona fasciculata plus zona reticularis in the Cd-treated rats on Days 3, 8, and 18.     

Influence of simultaneous exposure to acrylonitrile and styrene on the toxicity and metabolism of styrene in rats

Nine groups of adult male rats were given different combinations of styrene and acrylonitrile and each chemical was administered at three doses (styrene 0, 5.8, and 11.6 mmol/kg, ip; acrylonitrile 0, 0.3, and 0.6 mmol/kg, po). The animals were killed 24 hr later and blood and urine samples were collected. The results of biochemical analyses due to the toxicity of both chemicals and of the determination of urinary metabolites of styrene were then subjected to a factorial (3 X 3) analysis of variance. There was: (1) a significant elevation of blood urea nitrogen (BUN) and serum glutamic-pyruvic transaminase (SGPT), and a diminution of urinary creatinine due to styrene; (2) an increase in serum creatinine and serum glutamicoxaloacetic transaminase (SGOT) due to styrene that was further increased by acrylonitrile; and (3) an increase in the concentrations of urinary metabolites (thioethers, mandelic, phenylglyoxylic, and hippuric acids) due to styrene that was considerably reduced by acrylonitrile. These results suggest that styrene causes renal toxicity which may be potentiated by acrylonitrile; furthermore, the significant diminution of the urinary metabolites of styrene due to acrylonitrile obscures interpretation of the results of the biological monitoring of exposure to styrene.     

Teratogenic effects of cholinergic insecticides in chick embryos I. Diazinon treatment on acetylcholinesterase and choline acetyltransferase activities

Teratogenic effects of diazinon were assessed morphologically and correlated with values determined by radiometric determinations for acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities. Diazinon, at doses ranging from 23 to 1854 μg/chick egg, was injected on Day 3 of incubation, and enzyme activities in hindlimb, wing, and brain were measured on Days 6–20 of incubation. Generally, these organs displayed similar patterns of enzyme alteration. With an injected dose of 200 μg diazinon per egg, AChE activity was inhibited about 90% at Days 6–8, about 50% at Day 10, and not at all at Day 13. On the other hand, ChAT activity was not significantly different between diazinon- and corn oil-injected embryos. The threshold dose for type II teratogenic signs (such as wry neck and short neck) was higher than for type I signs (such as micromelia and abnormal feathering). Morphological studies, using atropine and gallamine, suggested that nicotinic but not muscarinic receptors may be involved in the mechanism of diazinon-induced type II malformations. Nicotinamide, which prevented type I malformations, did not prevent the diazinon-induced AChE inhibition. From the above findings, we confirm and extend the finding of others, that the cholinergic dysfunction does not temporally correlate with the type I teratogenic effects.     

Time course of cadmium-induced ultrastructural changes in rat liver

Ultrastructural changes in rat liver were studied 1, 2, 4, 6, 8, and 10 hr after administration of a single, high dose of Cd (3.9 mg Cd/kg, iv) or after repeated administration of a lower dose (0.5 mg Cd/kg, sc, 6 days/week for 6 months). These dosing regimens have been previously shown to produce hepatotoxicity and result in large accumulations of Cd in liver. In addition to light and electron microscopy, plasma enzyme activities indicative of liver injury, namely alanine (ALT) and aspartate (AST) aminotransferase, were determined at the aforementioned times. One hour after an acute dose of Cd, electron photomicrographs of liver showed dilation of the rough endoplasmic reticulum with concomitant loss of membrane-associated ribosomes, nucleolar condensation, and an increase in the number of perichromatin granules. At later times (4 and 6 hr), ultrastructural changes included mitochondrial swelling associated with matrical inclusions, further dilation and vesiculation of rough endoplasmic reticulum, and presence of a fibrillar material within cytoplasm. In contrast to changes observed after single administration of Cd, the predominant hepatic lesions in rats injected repeatedly with the metal over 6 months were interstitial fibrosis, nuclear enlargement, and an increase in number and predominance of nucleoli. Ultrastructural evidence of nuclear alterations included condensation of nucleoli and an increase in the number of perichromatin granules. These results indicate that Cd interferes with hepatic protein synthesis early after injection of a large dose, and that further degenerative changes occur later and possibly in response to protein inhibition. Although severe degenerative changes in liver were not evident in rats chronically exposed to the metal, Cd-induced changes in nuclei and nucleoli also indicate the likelihood of altered protein synthesis.