Ultrastructural morphometric investigations on rat liver of young and adult rats after treatment with technical pentachlorophenol (PCP)

Pentachlorophenol-induced hemotoxicity diminishes antioxidant potential and oxidizes proteins, thiols, and lipids in rat blood: An in vivo study

Pentachlorophenol (PCP) is an excessively used wood preservative and pesticide, which has resulted in human exposure raising concerns about its potential toxic effects. This study is designed to evaluate the hemotoxicity of PCP in adult rats. Wistar rats were orally administered PCP (25-150 mg/kg bw) for five days while untreated (control) rats received corn oil. Animals were sacrificed, blood was taken and fractionated into plasma and red blood cells (RBC). PCP administration increased methemoglobin formation but decreased methemoglobin reductase activity. Significantly increased hydrogen peroxide level indicates initiation of oxidative stress condition in blood. PCP increased the oxidation of thiols, proteins and lipids, lowered glutathione levels, and compromised the antioxidant status of RBC in treated rats. Enzymes of the pathways of glucose breakdown, glycolysis and phosphogluconate pathway, were inhibited. Markers of liver damage were increased in the plasma of PCP-treated rats suggesting hepatotoxicity. This was confirmed by histopathological analysis of stained liver sections. Activity of xanthine oxidase, a reactive oxygen species (ROS) generating pro-oxidant enzyme, was increased. These hematological changes could be a result of the increased generation of ROS or direct chemical transformation by transient reaction species. These results show that PCP induces redox imbalance, diminishes antioxidant potential, inhibits metabolic pathways, and oxidizes cellular components in rat blood. This study suggests an elaborated possible molecular mechanism of PCP toxicity, and similar compounds so that methods can be devised to minimize its damaging effect.

Pentachlorophenol Poisoning

Despite being banned in many countries and having its use severely restricted in others, pentachlorophenol (PCP) remains an important pesticide from a toxicological perspective. It is a stable and persistent compound. In humans it is readily absorbed by ingestion and inhalation but is less well absorbed dermally. Its distribution is limited, its metabolism extensive and it is eliminated only slowly. Assessment of the toxicity of PCP is confounded by the presence of contaminants known to cause effects identical to those attributed to PCP. However, severe exposure by any route may result in an acute and occasionally fatal illness that bears all the hallmarks of being mediated by uncoupling of oxidative phosphorylation. Tachycardia, tachypnoea, sweating, altered consciousness, hyperthermia, convulsions and early onset of marked rigor (if death occurs) are the most notable features. Pulmonary oedema, intravascular haemolysis, pancreatitis, jaundice and acute renal failure have been reported. There is no antidote and no adequate data to support the use of repeat-dose oral cholestyramine, forced diuresis or urine alkalinisation as effective methods of enhancing PCP elimination in poisoned humans. Supportive care and vigorous management of hyperthermia should produce a satisfactory outcome. Chronic occupational exposure to PCP may produce a syndrome similar to acute systemic poisoning, together with conjunctivitis and irritation of the upper respiratory and oral mucosae. Long-term exposure has also been reported to result in chronic fatigue or neuropsychiatric features in combination with skin infections (including chloracne), chronic respiratory symptoms, neuralgic pains in the legs, and impaired fertility and hypothyroidism secondary to endocrine disruption. PCP is a weak mutagen but the available data for humans are insufficient to classify it more strongly than as a probable carcinogen.

Cytological and biochemical effects of a mixture of 20 pollutants on isolated rainbow trout (Oncorhynchus mykiss) hepatocytes

Isolated hepatocytes of rainbow trout (Oncorhynchus mykiss) were exposed to different concentrations (1x, 10x, 50x) of a complex mixture of 20 environmentally relevant contaminants (PAHs, PCBs, pesticides) typical of the chemical burden of surface waters and sediments of small rivers in southwest Germany to investigate sublethal cytological and biochemical alterations. Results document that all concentrations clearly induced biochemical and morphological changes. The activities of enzymes such as lactate dehydrogenase and catalase as well as the rate of lipid peroxidation were significantly increased, whereas acid phosphatase activity decreased. Cytopathological effects included deformation of cellular shape, deformation and dilation of the nuclear envelope, increase in heterochromatin, nuclear inclusions, heterogeneity of mitochondria, vesiculation of RER cisternae, as well as increases in myelinated bodies, lysosomes, and peroxisomes. If compared with cytological alterations induced in isolated rainbow trout hepatocytes after exposure to sediment extracts from rivers of corresponding contamination, cytological effects of exposure to the complex chemical mixture displayed numerous similarities.

Effect of three chlorinated pesticides on hsromega stress gene in transgenic Drosophila melanogaster

Expression of hsromega stress gene in the third-instar larvae of 951-lacZ2 (hsromega-lacZ having-844pb sequence) and 498-lacZ1 (hrsomega-lacZ having -498bp sequence) strains of Drosophila melanogaster at LC(50) and lower dietary concentrations of hexachlorocyclohexane (HCH) pentachlorophenol (PCP), and endosulfan was examined in relation to larval mortality by beta galactosidase activity, vital dye staining, and salivary gland polytene chromosome puffing. Our results showed that both HCH and PCP at lower concentrations evoked strong hsromega stress gene expression in the larval tissues while endosulfan did not. On the other hand, puffing data revealed that endosulfan at lower doses, induced well-developed puff at the resident site (93D) of the hsromega gene but the transgenic sites (30B in 951-lacZ2 and 44B in 498-lacZ1 strain) did not show any well-developed puff. Regression in hsromega stress gene expression in 951-lacZ2 strain at LC(50) concentrations of HCH and PCP after 48 h was concurrent with extensive tissue damage as evident by trypan blue staining. Similarly, strong hsromega expression was accompanied by insignificant trypan blue staining in the larval tissues of this strain after shorter duration of exposure (2-12 h) to these toxicants. Although endosulfan under similar experimental condition did not induce hsromega, strong trypan blue staining indicated extensive tissue damage after 48 h of exposure. The present study suggests that all the three toxicants pose cytotoxic potential to Drosophila. While protective role of this stress gene was evident at the initial stages of exposure, extensive tissue damage in the later stages of intoxication accompanied by autorepression of hsromega led to larval mortality. The study further suggests that -844bp upstream sequence of the gene is adequate for hsromega inducibility against HCH and PCP but not for endosulfan for which responsive elements may be searched further upstream.

Effects of pentachlorophenol (PCP) on the pituitary and thyroidal hormone regulation in the rat

Investigations on rats after repeated application of pentachlorophenol (PCP) should clarify whether thyroid side effects caused by this xenobiotic can be seen in a dose range which does not cause major toxic effects. Female rats of the Wistar strain were treated with 3 and 30 mg PCP/kg body wt. daily by gavage for 28 days. To assess the potential impact of impurities the study was performed both with pure and technical grade PCP at the dosage of 3 mg.kg-1.day-1, and at a level of 30 mg.kg-1.day-1 with pure PCP only. The effects in animals on normal iodine diet were compared to those in animals on a low iodine diet. No decrease of body wt. was noticed, only the liver weights were increased slightly in animals treated with 30 mg.kg-1.day-1 PCP. However distinct effects on thyroid hormones as well as on thyrotropin (TSH) were observed: a pronounced fall of circulating thyroxine (T4) and triiodothyronine (T3) levels was accompanied by lower levels of both free thyroid hormones and TSH, and the T4:T3 ratio was decreased in serum. Furthermore the intrathyroidal hormone stores were reduced. An interference of PCP at pituitary or hypothalamic level is assumed as a major mode of action. Additional effects of the test substance on peripheral conversion can be suspected.

Light and electron microscopical changes in the liver of mice following treatment with aminotriazole

Light and electronmicroscopical alterations in the liver of mice were shown oral administration of aminotriazole. Intensity of damage depends on concentration. High dosage affects all inter- and intralobular portions. Presented light microscopical results show, next to an extreme hypertrophy of hepatocytes, well distinguishable nuclear deformations and increased pyknotic nucleoli. The cytoplasm contains numerous vacuoles and lipid droplets. Fine structural alterations after drug administration include defects on all cell organelles and membranes. Especially proliferations of smooth ER cisternae with simultaneous reductions of rough ER cisternae, increase of microbodies as well as numerous defects on mitochondria were obvious. Interpretations of the mode of action of aminotriazole is based on ultrastructural results and biochemical knowledge on this herbicide and compared with other toxicants.

Long-term study of liver damage following subcutaneous injection of airborne particle extracts and polycyclic aromatic hydrocarbon fractions

Female NMRI mice aged 9-12 weeks were each given a single subcutaneous injection of 0.5 ml of a suspension containing either the total extracts or the polycyclic aromatic hydrocarbon (PAH) fraction of airborne particles. Both the total extracts and PAH fractions contain 3 microgram benzopyrene. After about 15 months the livers were removed from the animals, which had by that time developed tumors at the injection site, and were subjected to electron-microscopical study. The essential alterations were observed in the nucleoli and the cell nuclei, which had greatly proliferated and exhibited irregular nuclear membranes. Advanced fibrosis was observed in central liver specimens of all groups. Marked alterations were also observed in the mitochondria and the mitochondrial cristae as well as in the bile canaliculi, Intracytoplasmic glycogen usually occurred densely clustered along the periphery of the cell. It may be concluded from the observations that both the total extract of atmospheric suspended particulate matter and the PAH fraction cause hematogenic damage to the liver following subcutaneous injection, a finding which cannot be interpreted as metastatic carcinoma.

Combined effects of vinblastine and vincristine on mouse hepatocytes with respect to ultrastructural elements

The results of a single dose of the microtubule-destroying agents vinblastine/vincristine (0.5 mg/0.05 mg) on the ultrastructural elements of mouse hepatocytes was studied using the techniques of thin-sectioning and freeze-fracture following intravenous injection of the drugs. Several cytoplasmic modifications were observed in the hepatocytes. These included the storage of lipid droplets, a heavy accumulation of autophagosomes and vacuoles with very low density lipoprotein (VLDL)-like vesicles, large glycogen fields and dilated intercellular spaces with intrahepatocytic vacuoles. The rough endoplasmic reticulum exhibited pathological changes with loss of ribosomes and the bile canaliculi exhibited in some cases the loss of microvilli as well as dilatation of the lumen. The tight junctions surrounding the bile canaliculi exhibited alterations as well. The strands were reduced in number and showed a less organized arrangement. The gap junction showed an increase in size as well as an irregular outline in contrast to controls. These findings are interpreted as non-specific toxic phenomena. However, the possibility cannot be precluded that certain phenomena, such as alterations in the cell junctions, may be attributable to specific microtubule-destroying properties of the drugs.