Proliferation Of Smooth Endoplasmic Reticulum Research Articles

Ultrastructural study of hepatic regeneration following one-lobe, two-lobe, and subtotal hepatectomy in the rat

The sequential and comparative ultrastructural features of regenerating rat liver following one-lobe, two-lobe, and subtotal hepatectomy were studied. All three groups demonstrated glycogen depletion at the 12 h post-hepatectomy interval with reaccumulation occurring at 24 h in the first two groups but not until 72 h in the subtotal hepatectomy group. Other hepatocellular alterations attributed to regenerative activity were similar in the three groups, however the onset and magnitude of those changes occurring in the two-lobe and subtotally hepatectomized rats differed significantly from those alterations occurring in the one-lobe hepatectomy group. These changes were characterized by a greater and more prolonged mitotic activity, increased proliferation of RER and smooth endoplasmic reticulum (SER), and by increased Golgi bodies. These two groups also manifested greater hepatocellular accumulation of phagolysosomes, myelin figures, and lipid bodies when compared with the one-lobe hepatectomy group.

Correlation of cadmium-induced nephropathy and the metabolism of endogenous copper and zinc in rats

Female Wistar rats were injected (sc) every second day for 8 weeks with Cd (0.25 mg/kg) as CdCl 2. After only a 2-week exposure, when cadmium (Cd) concentration in liver was about 13 μg/g, ultrastructural examinations revealed some irregular ergastoplasm systems and significant proliferation of smooth endoplasmic reticulum in the hepatocyte ultrastructure. The increase in Zn content occurred simultaneously with the increase in Cd concentration in the liver (Zn to Cd ratio was 1:1). In the kidneys after a 3-week exposure, when Cd concentration was 7 μg/g, the concentration of endogenous Cu increased. At the same time the urinary excretion of that metal was considerably higher than that of the control group. In the kidneys after a 4-week exposure, when Cd concentration in this organ exceeded 10 μg/g tissue, injured brush border microvilli and swollen mitochondria in the proximal convoluted tubular cells were seen. In renal corpuscules, fusion between the podocyte pedicles was also found. The changes in renal cortex ultrastructure became more pronounced when Cd concentration in kidney was increasing. Necrotic changes in the examined organ were observed when Cd concentration increased to about 30 μg/g tissue. The critical concentration in renal cortex of about 200 μg/g tissue should be revised. The present margin of safety with regard to risk of renal effects is small.

The effect of combined exposures to ethanol and xylene on rat hepatic microsomal monooxygenase activities

Studies on rats treated for 8 months with ethanol (10% solution in drinking water) and simultaneously exposed to xylene vapour (12.000 mg/m 3, 5 hr daily) for the last 9 days revealed that the chemicals exert additive stimulatory effect on hepatic microsomal monooxygenases: the activity of aniline p-hydroxylase increased by 380%, microsomal ethanol oxidizing system by 92%, NADPH-cyt. c reductase by 30% and the level of cytochrome P-450 by 70%. The changes were accompanied by a marked proliferation of smooth endoplasmic reticulum (a subcellular site of cytochrome P-450 monooxygenases in the hepatocytes) and an increased NADPH-Fe 2+- and ascorbate-Fe 2+-driven lipid peroxidation in microsomal membranes—a potential toxic mechanism. Interaction of ethanol and xylene with cytochrome P-450 monooxygenases may enhance metabolic capacity of the liver and in consequence modify biological/toxic effects of occupational exposure to solvents in the case of alcohol abuse.

Sex-specific reaction of liver ultrastructure in zebra fish ( Brachydanio rerio) after prolonged sublethal exposure to 4-nitrophenol

Morphological alterations of the liver of zebra fish ( Brachydanio rerio) following prolonged exposure to 0.1, 1 and 5 mg · l −1 4-nitrophenol (4-NP) were investigated by means of light and electron microscopy. Based on marked sexual dimorphism in control animals, liver recactions were both sex- and dose-dependent. Whereas at 0.1 mg·1 −1 only minor changes could be revealed, there were numerous structural modifications at 1 mg·1 −1: Whereas male fish primarily react with a proliferation of smooth endoplasmic reticulum, female fish display a high degree of fenetrastion within cisternate of the rough endoplasmic reticulum. Both sexes exhibit infiltration of macrophages and lymphocytes, an increase in the number of binucleate cells, of lysosomes, autophagosomes and myelinated bodies, but a depletion of hepatic glycogen. At 5 mg·1 −1, deformations of the nuclear membrane and partial lysis of mitochondria could be observed. At 1 and 5 mg·1 −1 4-NP about 25% of the animals investigated showed symptoms of degenerative transformations of the liver tissue into huge multinucleate cell masses with completely different ultrastructure. The evaluation of the results leads us to the conclusion that for toxicological studies on the effects of ‘priority pollutants’ histological and cytological investigations should be incorporated into an integrated methodological scheme.

Inhibitors of sterol synthesis. Morphological studies in rats after dietary administration of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a potent hypocholesterolemic compound.

The morphological effects of short-term (9 days) dietary administration (0.1% in a laboratory chow diet) of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a novel regulator of cholesterol metabolism with significant hypocholesterolemic activity, has been studied in young male rats. Control animals included rats fed the basal diet ad libitum and a series of rats pair-fed to the individual experimental animals. At the time of necropsy, the morphological changes in rats which have been observed in rats following treatment with other absorbable hypolipidemic agents (myeloid bodies with triparanol, increased peroxisomes with clofibrate, and proliferation of smooth endoplasmic reticulum with compactin and mevinolin) were not apparent on ultrastructural examination of livers of rats treated with the 15-ketosterol. Two changes were observed in the rats fed the 15-ketosterol: a decrease in adipose tissue and enlargement of the small intestine. Diminished fat was also noted in the pair-fed controls and was presumably due to decreased food consumption. The intestines of rats fed the 15-ketosterol were morphometrically most enlarged in the jejunal region. Morphologically, this increase was distinguished by increased depth of crypts of Lieberkuhn and pseudostratification of epithelium at the base of the villi. These changes were qualitatively and quantitatively similar to the adaptive changes reported in the rat after resection of small bowel or following intestinal bypass (segment of bowel remaining in continuity). The morphological changes induced in the rat by administration of the 15-ketosterol were not observed in 4 baboons which received the compound orally at doses of 50, 75, or 100 mg per kilogram of body weight for up to 3 months.

Thirteen-week oral toxicity study of propiverine hydrochloride in dogs

A subacute oral toxicity study of propiverine hydrochloride (P-4), a new anti-pollakiuria agent, was carried out at dose-levels of 0, 1, 3, 9, and 27 mg/kg/day using male and female beagle dogs. They were treated for 13 weeks, followed by 5 weeks recovery period. The results obtained from the present study were as follows. 1. In the observation of general symptoms, mydriasis was observed in females receiving 3 mg/kg/day or more and in males receiving 9 mg/kg/day or more, every day, intermittently or sporadically. The incidence of mydriasis varied greatly in individuals. However, this sign disappeared within administration period. 2. Body weight gain was slightly suppressed in males and females receiving 27 mg/kg/day. 3. There were no significant changes in food consumption, water consumption, hematology, urinalysis and fecal occult blood, and no remarkable changes in ophthalmology, electrocardiogram. 4. Serum biochemical findings showed a decrease in Total cholesterol (T. cho), Free cholesterol (F. cho), Triglyceride (TG), Phospholipid (PL), Total protein (TP), Albumin (ALB), alpha 1-Globulin (alpha 1-GLO) and Calcium (Ca), and an increase in Alkaline phosphatase (Al P), gamma-Glutamyltranspeptidase (gamma-GTP) activities and Choresterol ester ratio (EST/T) in males and females receiving 27 mg/kg/day. Further, a decrease in lipoprotein-T. cho, -TG and -PL were noted, on the other hand, lipoprotein-T. cho, -TG and -PL in the liver tissue increased. Similar slight changes were observed in males and females receiving 9 mg/kg/day. 5. Pathological examination revealed an enlargement of hepatocytes in a few animals receiving 3 mg/kg/day. In males and females receiving 9 mg/kg/day or more, yellowish liver, a increase in liver weights, an enlargement of hepatocytes with fatty degeneration and the appearance of eosinophilic inclusions in the hepatocytes were observed. Furthermore, some males and females receiving 27 mg/kg/day showed a slight cellular infiltration in glisson's sheaths, proliferation of the bile ducts and deposition of lipid droplets. Histochemical examination of liver tissue showed an increase in Al P and gamma-GTP activities in addition. Electronmicroscopically, the proliferation of smooth endoplasmic reticulum, increases in myelin-like inclusions and small lipid droplets in the hepatocytes were noted and these changes suggested the induction of drug-metabolizing enzyme in the liver. 6. After 5 weeks recovery period, above-mentioned changes were disappeared and it was suggested that these were reversible ones. 7. From the above results, the non-effective dose and the toxic one were estimated to be 1 mg/kg/day and 9 mg/kg/day for males and females, respectively.

Thirteen-week oral toxicity study of propiverine hydrochloride in rats

A subacute toxicity study of propiverine hydrochloride (P-4), a new anti-pollakiuria agent, was carried out using male and female Wistar rats. P-4 was orally administered to rats at dose levels of 2, 10, 50 and 150 mg/kg/day for 13 weeks, followed by 5 weeks recovery period. The results obtained are as follows: 1. In the general conditions, transient salivation was observed immediately after administration and blotted fur at lower abdomen was noted in rats given 50 mg/kg/day or more. There were no deaths related to P-4. 2. Body weight gain was depressed in males given 50 mg/kg/day or more and females given 150 mg/kg/day. No significant changes in food consumption were observed. Water consumption increased in the groups of 50 mg/kg/day or more. 3. Urinalysis revealed an increase of urine volume, decreases of osmotic pressure, protein and urobilinogen, and a slight increase in excretion of electrolyte in rats given 50 mg/kg/day or more. 4. Hematological examinations revealed slight changes such as an increase in erythrocyte count and a shortening of APTT in rats given 150 mg/kg/day. 5. Serum biochemical examinations showed a decrease in triglyceride and increases in gamma-GTP and AlP activities, and urea nitrogen in males given 50 mg/kg/day or more and females given 150 mg/kg/day. Additionally, decreases in total and free cholesterol, and phospholipid for males and an increase of total cholesterol and a decrease of cholinesterase activity for females were detected. 6. At autopsy, atrophy of thymus and spleen was observed in rats given 50 mg/kg/day or more, but without histopathological correlation. Histopathological examinations revealed hypertrophy and fatty degeneration of hepatocytes, which were accompanied with increases of absolute and/or relative liver weight, in males given 50 mg/kg/day or more and females given 150 mg/kg/day. Electron-microscopy showed proliferation of smooth endoplasmic reticulum in the same groups. In the kidney, eosinophilic and intranuclear inclusions in the tubular epithelium were detected, in which cytoplasm there were no toxic injuries, in males given 10 mg/kg/day or more and females given 50 mg/kg/day or more. 7. After 5 weeks recovery period, above-mentioned changes were generally disappeared, suggesting that these were reversible. 8. The non-effective dose levels and the toxic dose levels of P-4 were estimated to be 2 mg/kg/day for males and 10 mg/kg/day for females, and 50 mg/kg/day for males and 150 mg/kg/day for females, respectively.

Dithiobiuret neurotoxicity: an ultrastructural investigation of the lesion in preterminal axons and motor endplates in the rat lumbrical muscle

2,4-Dithiobiuret was given i.p. to rats for 4 days at a daily dosage of 1 mg/kg and the development of the lesion associated with neuromuscular dysfunction studied in hindlimb lumbrical muscles. The first morphological indication of neurointoxication was the appearance in some motor endplates of masses of branching tubular smooth endoplasmic reticulum (SER) on day 2 which correlated with the initial functional disturbances. By the 3rd day, most motor endplates were distended by accumulations of dense-cored, lucent and synaptic vesicles, abnormally swollen mitochondria, intermediate filaments and branching, tubular SER. Evidence of collateral axonal sprouting was seen first at this time. On days 4 and 5, many motor endplates were markedly enlarged and showed axoplasmic organelle congestion. A significant increase in synaptic vesicle size was noted at these times in some terminals. Interposition of Schwann cell processes between the pre- and postsynaptic membranes and terminal retraction was now evident. Some intramuscular nerves showed hydropic Schwann cell cytoplasm with separation of the outermost myelin lamellae, mitochondrial swelling and adaxonal vacuoles as early as the 1st day. Proliferation and segregation of SER around central cores of neurofilaments was seen in myelinated nerve fibres and preterminals on the 3rd day. At this and later times accumulations of SER and swollen mitochondria were found at sites of axonal varicosities and at the paranodal constrictions at nodes of Ranvier. These ultrastructural data are discussed with regard to reduced terminal Ca2+ content (demonstrated by oxalate-pyroantimonate cytochemistry) and compared with the sequelae of botulinum intoxication.

Inhibitory effect of phenobarbital on peroxisome biogenesis in mouse hepatocytes

Peroxisomes in hepatocytes from mice administered 35, 50, or 100 mg/kg of phenobarbital (PB) were analyzed by quantitative electron microscopy. In perivenular hepatocytes, the volume of peroxisomes per unit cytoplasmic volume decreased to 78 or 57% of that of control animals by administration of 50 or 100 mg/kg. Their average volume also decreased to 78 or 64% of that in control animals in animals injected with 35 or 50 mg/kg. Further, cytochemical catalase activity appeared decreased in peroxisomes of hepatocytes of this zone after administration of 50 or 100 mg/kg. These suggest an inhibitory action of PB administration of biogenesis of peroxisomes in perivenular hepatocytes. In periportal hepatocytes, however, the volume density, average volume, and cytochemical catalase activity of peroxisomes did not change by administration of any doses of PB. Thus, PB administration appears to produce no inhibitory effect on the peroxisome biogenesis in periportal hepatocytes. On the other hand, the number of peroxisomes per unit cyto-plasmic volume increased in both periportal and perivenular hepatocytes in animals injected with 50 mg/kg, although it returned to the level of control animals by injection of 100 mg/kg. The inhibitory effect of PB on the peroxisome neogenesis in perivenular hepatocytes may be related to the marked smooth endoplasmic reticulum proliferation by administration of this drug.

Chronic toxicity and carcinogenic evaluation of permethrin in rats and mice

Groups of Alpk:AP (Wistar-derived) rats were fed diets containing 0, 500, 1000 or 2500 ppm permethrin for 2 years and Swiss-derived mice were maintained for their lifetime (80% mortality) on diets containing 0, 250, 1000, or 2500 ppm permethrin. Changes of toxicological significance were confined to the top dose level of 2500 ppm permethrin in both species. Tremors and hypersensitivity to noise were noted in rats at this dose during the first 2 weeks of study but such signs were not seen in mice. Pathological examination of the central and peripheral nervous systems did not reveal abnormalities attributable to permethrin administration. The effect on mice at 2500 ppm permethrin was shown by decreased body weight gain. Liver hypertrophy, associated with increase in liver weight, microsomal enzyme activity, and proliferation of smooth endoplasmic reticulum occurred in the rat with similar but less marked changes in the mouse. This was considered to be an adaptive response of no toxicological significance. No vidence of a carcinogenic effect was seen in the rat study. In the mouse study a slight elevation in benign lung tumor incidence in males only at 2500 ppm permethrin was observed but was not considered to represent a carcinogenic effect.

Effects of mevinolin, an inhibitor of cholesterol synthesis, on the morphological and functional responses of rat adrenal zona fasciculata to a prolonged treatment with 4-aminopyrazolo-pyrimidine.

Rat adrenocortical cells are almost completely dependent upon the continuous supply of cholesterol derived from serum lipoproteins. However, a prolonged (5-day) administration of 4-aminopyrazolo-pyrimidine (4-APP), a potent hypocholesterolaemic drug, though provoking a notable decrease in the intra-adrenal concentration of esterified and free cholesterol, did not significantly affect basal plasma level of corticosterone. Morphometry showed a conspicuous hypertrophy of zona fasciculata cells, coupled with a striking proliferation of smooth endoplasmic reticulum (SER) and peroxisomes and with a profound lipid-droplet depletion. The secretory response of zona fasciculata cells to ACTH was still present, but reduced by half with respect to control rats. The simultaneous administration of mevinolin, an inhibitor of cholesterol synthesis, to 4-APP-treated rats caused an additional drop in the intracellular content of free cholesterol and notably lowered basal plasma corticosterone concentration. Mevinolin magnified the 4-APP-induced zona fasciculata cell hypertrophy, as well as SER and peroxisome proliferation. The secretory response to ACTH was completely suppressed. These data are compatible with the view that the morphological changes, which rat zona fasciculata cells undergo during prolonged hypocholesterolaemia, are the expression of the activation of the endogenous cholesterol synthesis. This compensatory response, enabling zona fasciculata cells to maintain a normal basal rate of hormonal output and to respond (though less efficiently) to their main physiological stimulus, seems to be completely independent of any activation of the hypothalamo-hyphophyseal axis, since dexamethasone/ACTH treated rats were used. The hypothesis is advanced that the mechanism underlying this response may involve the decrease of the intracellular free-cholesterol pool.

Hepatotoxicity induced by the herbicide atrazine in the rat.

The hepatotoxicity of atrazine was investigated by studying clinical parameters related to hepatic function and by electron microscopy. Three groups to male albino rats (Wistar strain) received 100, 200 and 400 mg of atrazine/per kg of body weight/per day, for 14 days. One group received 600 mg atrazine/per kg of body weight/per day, for 7 days. At termination of dosing, the animals were sacrificed and blood was drawn for the determination of serum total lipids, glucose, alanine aminotransferase (ALT) and alkaline phosphatase (SAP). A dose dependent decrease in serum glucose concentration was observed in all the groups. In contrast, a dose relate increase in total serum lipids, was apparent at all dose levels studied. Activity of serum ALT and SAP increased approximately 60% and 200% respectively in rats given 600 mg atrazine/kg bw for 7 days. The liver was examined grossly and microscopically. Electron microscopy disclosed no changes in the hepatocytes of rats treated with the low dose (100 mg/kg bw). At high doses, electron microscopy revealed hepatocytic proliferation and degeneration of smooth endoplasmic reticulum, lipid accumulation and alteration of bile canaliculi proportional to dose and duration of treatment.

Acute biological effects of commercial cresyl diphenyl phosphate in rats

A commercial cresyl diphenyl phosphate preparation was analyzed to contain approximately 35% of triphenyl phosphate, 45% of cresyl diphenyl phosphates, 18% of dicresyl phenyl phosphates and 2% of tricresyl phosphates. The product was almost free of the o-cresyl isomers as revealed by the analysis of its alkaline hydrolysis products. A single intraperitoneal injection (150 or 3 mg/kg) caused an induction of microsomal cytochrome P-450 in the liver of Wistar rats with a concomitant increase in the activities of mixed function monooxygenases and proliferation of smooth endoplasmic reticulum 24 h after the treatment. These effects were not detected in the kidneys. The morphological changes in hepatocytes included the enlargement of nuclei and mitochondria with increased cristae. The hepatic morphology returned to normal 2 weeks after the treatment. The activity of pseudocholine esterase in blood was inhibited 4 h and 24 h after the injection but the effect levelled off. The concentration of the organophosphates in blood and liver decreased rapidly with only traces detected in blood after 24 h. No effects on the activities of cerebral and muscle acetylcholine esterase were observed. The treatment (300 mg/kg) inhibited the brain — 2′,3′-cyclic nucleotide 3′-phosphohydrolase through the 2-week observation period associated with demyelination in peripheral nerves.

Aminoglutethimide as an inducer of oxidative drug metabolism in the rat

There is some evidence that when aminoglutethimide is used in the treatment of patients with advanced breast cancer a clinically-significant degree of hepatic enzyme induction may occur. This activity of the drug has been investigated in female rats. After three daily oral doses (60 mg/kg) of aminoglutethimide, the hypnotic effect of hexobarbitone was significantly shortened and plasma levels of dicoumarol were lowered. This pretreatment regimen also diminished an estradiol-induced increase in uterine weight. Electron microscopy of liver from aminoglutethimide-treated rats revealed a proliferation of smooth endoplasmic reticulum. There were significant increases in the metabolism of 4-nitroanisole, dicoumarol and [ 14C]estradiol by the 10,000 × g supernatant of liver homogenates from aminoglutethimide-pretreated rats. In these animals, levels of hepatic microsomal protein, cytochrome P-450 and NADPH-cytochrome-C reductase were raised. The results are consistent with aminoglutethimide being a phenobarbitone-like inducer of the hepatic mixed-function oxidases.

Feline dysautonomia: an ultrastructural study of neurones in the XII nucleus.

A feline dysautonomia of unknown aetiology has been reported in numerous cats in the United Kingdom since 1981. The consistent histological lesion is a chromatolytic-type change within the neurones of the autonomic nervous system, which is also found less frequently in non-autonomic regions, such as the XII nucleus. This study describes the ultrastructural changes in the XII nucleus within the first 2 weeks of clinical disease. In the abnormal neurones there is a dispersion of the Nissl substance, progressing to dilation of individual cisternae by an electron-dense floccular material. Such cisternae have lost the majority of their ribosomes. Normal Golgi complexes can be seen in neurones where there is only slight dispersion of the Nissl substance, but no Golgi complexes, either normal or abnormal, can be identified in any cell in which the Nissl substance is markedly disrupted. There is proliferation of smooth endoplasmic reticulum in several neurones, and there may also be an increased number of morphologically normal mitochondria. The nuclei of affected neurones are eccentric with crenations of the nuclear envelope, and in some cases nucleolar changes are also observed. Autophagic vacuoles are present in small numbers. Other organelles appear normal. These findings compare closely to those for the autonomic neurones, suggesting that the primary effect of the causal agent(s) is on the protein synthetic pathway of specific neurones.

Localization of ultrastructural alterations induced in rat liver by dietary polybromobiphenyls (FireMaster BP-6).

In 1973 and 1974, widespread environmental pollution and animal losses in Michigan were caused by the accidental incorporation of polybrominated biphenyls (PBBs, FireMaster FF-1) in livestock feed. This study documents the deleterious changes in the liver during an early state of polybrominated biphenyl-induced toxicosis. Male weanling Fischer rats were fed diets containing either 0 or 100 ppm of polybromobiphenyls (Fire-Master BP-6) (PBBs) for 10 days. Dietary PBBs did not affect body weight or food consumption. At necropsy, the liver was removed and processed for light and electron microscopy. The livers of PBB-treated rats were enlarged and friable. Light microscopic changes included moderate enlargement of centrilobular and midzonal hepatocytes which exhibited a foamy cytoplasm. Periportal hepatocytes appeared normal except that most bile canaliculi were dilated. Ultrastructural alterations within centrilobular hepatocytes consisted of small and dense mitochondria, abundant smooth endoplasmic reticulum, deep stacks of rough endoplasmic reticulum which appeared disorganized with fewer attached ribosomes, numerous lipid droplets, and dilated bile canaliculi which often contained myelin-like figures. The ultrastructural changes within mid-zonal hepatocytes were similar to centrilobular hepatocytes except there was less proliferation of smooth and rough endoplasmic reticulum, larger and less dense mitochondria, and more numerous lipid droplets which varied greatly in size. Glycogen depletion was apparent in both centrilobular and midzonal hepatocytes as was numerous multi-vesicular bodies associated with the Golgi apparatus.

Effect of subchronic dietary administration of butylated hydroxyanisole on canine stomach and hepatic tissue

Beagle dogs, 29 males and 30 females, were assigned to feeding groups of 0, 1.0 and 1.3% butylated hydroxyanisole (BHA) for 180 days. Animals were observed, daily for physical signs of pharmacological or toxicological effect. Except for the production of a reddish-brown urine, no physical signs attributable to BHA administration were observed. Both food consumption and body-weight gain were reduced in the BHA-treated animals. Fifty-one animals completed the study. At termination, tissues were examined for gross BHA-related effects, and specimens were taken for enzyme analysis, light microscopy, electron microscopy and morphometric analysis. The liver showed a significant weight increase over the control in both sexes at both BHA dose levels. Ultrastructural examination of the liver of BHA-treated animals revealed proliferation of smooth endoplasmic reticulum and hepatocytic cytoplasmic myelinoid bodies. Enzyme analysis of hepatic tissue showed a significant increase in mixed-function oxidases, UDP glucuronyl transferase, glutathione S-transferase and epoxide hydratase in the BHA-treated dogs compared with the controls. Light microscopy revealed no proliferative/hyperplastic lesions of the stomach/gastric epithelium. Electron microscopic examination of the lower oesophagus and stomach specimens from representative animals from each treatment group failed to reveal any treatment-related effect as compared with controls.

Quantitative analysis of smooth and rough endoplasmic reticulum proliferation in differentiating hepatocytes of midpostnatal mice treated with phenobarbital

The increase, expressed as a percentage of the control value, in the area of smooth endoplasmic reticulum (ER) per unit cytoplasmic volume did not differ between periportal and perivenular hepatocytes in 10-day-old mice injected with 50 mg/kg phenobarbital (PB) at 7, 8, and 9 days of age, whereas it was greater in perivenular than in periportal hepatocytes in 20-day-old animals injected with 100 mg/kg at 17, 18, and 19 days of age. Unexpectedly, the amount of rough ER increased after PB administration in both perivenular and periportal hepatocytes in the two age groups. Experiments done to determine the significance of the rough ER proliferation brought the following results. The intensity of immunohistochemical fluorescence for albumin decreased in both periportal and perivenular hepatocytes from 20-day-old animals treated with PB. NADPH-cytochrome c reductase activity increased in both smooth and rough microsomes in 20-day-old animals treated with PB. These results show that the predominant proliferation of smooth ER in perivenular hepatocytes after PB administration, characteristic of adult liver, arises between 10 and 20 days of age, and that rough ER proliferation, which is related to the increase in drug metabolism, is characteristic of the liver of midpostnatal mice.

Combined effect of ethanol and carbon disulphide on cytochrome P-450 mono-oxygenase, lipid peroxidation and ultrastructure of the liver in chronically exposed rats.

A 5-month treatment of rats with ethanol (10% solution in drinking water) stimulated aniline p-hydroxylase and the microsomal ethanol oxidizing system (MEOS) by 140 and 70%, respectively, cytochrome P-450 by 22% and accompanied by lipid peroxidation by 40% in microsomes. It also caused smooth endoplasmic reticulum (SER) proliferation and rough endoplasmic reticulum (RER) degranulation in hepatocytes. Repeated inhalatory exposure of rats to 1.5 g/m3 of CS2, 5 h daily, 5 days a week for 5 months decreased aniline p-hydroxylase and MEOS by 70 and 55% respectively, doubled hexobarbital sleeping time and depressed cytochrome P-450 by 30% and its conversion to cytochrome P-420; these effects were accompanied by the appearance of cytochrome P-420, the intensification of lipid peroxidation in microsomes and some degranulation of RER in hepatocytes. Combined exposure of rats to ethanol and CS2 resulted in a significant potentiation of the inhibitory effects of CS2 on cytochrome P-450 mono-oxygenase and MEOS but with enhancement of CS2 effects on the liver microsomal mono-oxygenase, but CS2 decreased the effect of ethanol on SER proliferation. The interaction both on the biochemical and the morphological level can be explained with the ethanol-stimulated biotransformation of CS2 to reactive electrophilic derivative(s), the subsequent destruction of cytochrome P-450 to cytochrome P-420 and the intensification of lipid peroxidation.

The subchronic oral toxicity of the β-isomer of hexachlorocyclohexane in rats

The 13-week oral toxicity of β-HCH, a nonpesticidal isomer of hexachlorocyclohexane, was investigated in rats with doses of 0, 2, 10, 50, or 250 mg/kg feed. Parameters studied comprised clinical signs, growth and food intake, biochemistry, hematology, organ weights, and histopathology. In all dose groups liver effects comprising increase of organ weight, centrilobular hepatocytic hypertrophy, and proliferation of smooth endoplasmic reticulum or increased activity of microsomal enzymes, were observed. In the 50 mg/kg group the weights of thymus and testes were affected. In the highest dose group, progressive clinical signs leading to the unscheduled sacrifice of approximately 50% of the rats were observed. Moreover, in the males of this group atrophy of the testes, characterized by a reduced size of the seminiferous tubules and a decreased number of interstitial cells was observed in association with spermatogenic arrest. The females in this group showed atrophy of the ovaries with impaired oogenesis and focal hyperplasia and metaplastic changes of the endometrial epithelium. These effects are discussed with respect to a possible estrogenic action of β-HCH.