Experimental hepatic porphyria induced by polychlorinated biphenyls

The elderly as a sensitive population in environmental exposures: making the case

The US population is aging. CDC has estimated that 20% of all Americans will be 65 or older by the year 2030. As a part of the aging process, the body gradually deteriorates and physiologic and metabolic limitations arise. Changes that occur in organ anatomy and function present challenges for dealing with environmental stressors of all kinds, ranging from temperature regulation to drug metabolism and excretion. The elderly are not just older adults, but rather are individuals with unique challenges and different medical needs than younger adults. The ability of the body to respond to physiological challenge presented by environmental chemicals is dependent upon the health of the organ systems that eliminate those substances from the body. Any compromise in the function of those organ systems may result in a decrease in the body's ability to protect itself from the adverse effects of xenobiotics. To investigate this issue, we performed an organ system-by-organ system review of the effects of human aging and the implications for such aging on susceptibility to drugs and xenobiotics. Birnbaum (1991) reported almost 20 years ago that it was clear that the pharmacokinetic behavior of environmental chemicals is, in many cases, altered during aging. Yet, to date, there is a paucity of data regarding recorded effects of environmental chemicals on elderly individuals. As a result, we have to rely on what is known about the effects of aging and the existing data regarding the metabolism, excretion, and adverse effects of prescription medications in that population to determine whether the elderly might be at greater risk when exposed to environmental substances. With increasing life expectancy, more and more people will confront the problems associated with advancing years. Moreover, although proper diet and exercise may lessen the immediate severity of some aspects of aging, the process will continue to gradually degrade the ability to cope with a variety of injuries and diseases. Thus, the adverse effects of long-term, low-level exposure to environmental substances will have a longer time to be manifested in a physiologically weakened elderly population. When such exposures are coupled with concurrent exposure to prescription medications, the effects could be devastating. Public health officials must be knowledgeable about the sensitivity of the growing elderly population, and ensure that the use of health guidance values (HGVs) for environmental contaminants and other substances give consideration to this physiologically compromised segment of the population.

Urinary porphyrin excretion in normal children and adolescents

BACKGROUND

Urinary porphyrins are diagnostic of various metabolic disorders and xenobiotic exposures, but comprehensive normative data for urinary porphyrin concentrations in children are currently unavailable.

METHODS

Subjects were participants in a prospective, randomized, controlled clinical trial of dental materials safety, 8 to 12 y at inception, who were followed longitudinally for 7 y after baseline with an extensive battery of neurobehavioral, neurological, renal function and urinary porphyrin assessments. Porphyrins were quantified by HPLC. Linear regression analyses were used to measure associations of porphyrin levels with age and gender.

RESULTS

Mean concentrations, 95% confidence intervals, and 10th, 50th, and 90th percentiles for all 5 typically excreted urinary porphyrins are presented by year of age and by gender. Unadjusted urinary concentrations (microg/l) of all 5 porphyrins remained relatively constant throughout the age range of 8-18 y for both males and females. In contrast, creatinine-adjusted urinary porphyrin concentrations (microg/g) declined significantly throughout this age range in both genders. Boys had significantly higher pentacarboxyl- and copro-porphyrin levels compared with girls both before and after creatinine adjustment.

CONCLUSIONS

Normative longitudinal data provided herein may facilitate the clinical assessment of pediatric metabolic disorders and may be of particular relevance in evaluating porphyrin changes as a biological indicator of disease or xenobiotic exposures among children and adolescents.

Attenuation of polychlorinated biphenyl induced uroporphyria by iron deprivation

A toxic sequel to polyhalogenated aromatic hydrocarbon exposure in humans is the development of porphyria cutanea tarda. In a mouse model (experimental uroporphyria) utilizing an environmentally relevant polychlorinated biphenyl (PCB) mixture, we show that the toxicity can be markedly influenced by nutritional status. In mice made susceptible to uroporphyria through a targeted deletion of one allele of uroporphyrinogen decarboxylase (Uro-D+/-), an iron deficient diet prevented the development of the uroporphyria and the changes in associated parameters normally seen within three weeks following a single exposure to Aroclor 1254. Iron deprivation also completely prevented PCB-induced uroporphyria in mice wild-type at the Uro-D locus (Uro-D+/+), a model that requires δ-aminolevulinic acid administration for the development of uroporphyria. In Uro-D+/- mice consuming δ-aminolevulinic acid, PCB exposure produced a severe uroporphyria that was attenuated, not prevented, by iron deficiency. This attenuation moderated hepatic uroporphyrin and uroporphyrinogen decarboxylase inhibitor levels, but not the depression of cytosolic uroporphyrinogen decarboxylase activity.

Uroporphyria in the uroporphyrinogen decarboxylase-deficient mouse: Interplay with siderosis and polychlorinated biphenyl exposure

Several methods have been used to develop rodent models with the hepatic manifestations of porphyria cutanea tarda (PCT). Acute iron administration or mutations of the hemochromatosis gene (Hfe) have been used to generate hepatic siderosis, a nearly uniform finding in PCT. Heterozygosity for a null mutation at the uroporphyrinogen decarboxylase (Uro-D+/-) locus has been developed to mimic familial PCT in humans. This study examines the interplay of these 2 genetic risk factors and their influence, alone and combined with polychlorinated-biphenyl exposure. Neither an Hfe-null mutation nor iron-dextran administration alone or in combination with polychlorinated biphenyl exposure was porphyrinogenic in a 3-week model using mice wild-type at the Uro-D locus. Homozygosity for an Hfe-null mutation significantly elevated hepatic iron but not to the extent seen with parenteral iron-dextran administration. Homozygosity for an Hfe-null mutation but not iron-dextran administration was porphyrinogenic in animals heterozygous for the Uro-D mutation. Polychlorinated biphenyls were also porphyrinogenic in these animals. Uroporphyria in Uro-D+/- animals was exacerbated by combinations of the homozygous Hfe-null mutation and polychlorinated biphenyls and iron-dextran and polychlorinated biphenyls. In all cases in which uroporphyria developed, a greater degree of experimental uroporphyria was seen in female animals. All elevated hepatic uroporphyrin concentrations were accompanied by depressed uroporphyrinogen decarboxylase activity and the presence of a factor in cytosol that inhibits recombinant human uroporphyrinogen decarboxylase. In conclusion, the expression of the uroporphyric phenotype, dependent on the susceptibility imparted by a genetic mutation, provides a uniquely facile model for dissecting the molecular pathogenesis of the disease.

Hepatocellular iron accumulation and increased cell proliferation in polychlorinated biphenyl-exposed Sprague-Dawley rats and the development of hepatocarcinogenesis

Polychlorinated biphenyls (PCBs) are liver-tumor promoters in rodents, but the underlying mechanisms have not been fully elucidated. Tissue sections from the PCB bioassay reported by Mayes et al. 1998, Toxicol Sci., 41-66, were evaluated by histopathological techniques that included immunohistochemistry. In females, and to a much lesser extent in males, iron accumulation in hepatocytes was found at the 26th-week sacrifice, which was pronounced in the mid- and high-dose Aroclor-1254 and -1260 groups. At 52 weeks, large accumulations of iron were also present in Kupffer cells of females, and dose-related increases in proliferating cell nuclear antigen (PCNA) hepatocyte labeling indices were found in both males and females. These changes preceded the formation of liver tumors, which were not generally found until 78 weeks. Glutathione S-transferase placental (GSTP) positive foci were present at 52 weeks in high-dose Aroclor-1254 and -1260 female groups, and small foci were found in some Aroclor 1254-exposed female rats at 26 weeks, along with centrilobular hepatocytes expressing GSTP. The results of this study suggest that PCB-induced iron accumulation in hepatocytes is an early event that may be related to tumor formation, especially in female rats. In both males and females, increases in cell proliferation at 52 weeks were statistically significantly correlated with tumor incidences at termination among the various PCB dosage groups. Consequently, iron accumulations producing oxidative damage, and enhanced cell proliferation resulting in tumor promotion may be components in the mode of action for PCB-induced hepatocarcinogenesis in rodents.

Irgasan DP 300 (5-chloro-2-(2,4-dichlorophenoxy)-phenol) induces cytochrome P450s and inhibits haem biosynthesis in rat hepatocytes cultured on Matrigel

1. The effect of Irgasan DP 300 (5-chloro-2-(2,4-dichlorophenoxy)phenol) on cytochrome P450 (P450) induction and haem biosynthesis was studied in rat hepatocytes cultured on Matrigel. 2. Irgasan DP 300 significantly induced 7-benzyloxyresorufin O-debenzylase activity, followed by 7-pentoxyresorufin O-depentylase and 7-ethoxyresorufin O-deethylase activities. 4-Nitrophenol hydroxylase, testosterone 6 beta-hydroxylase and methoxyresorufin O-demethylase activities were also slightly increased. The maximum induction of these enzyme activities was obtained at the same concentration of 125 microM in the culture medium. 3. Immunochemical blots using anti-rat cytochrome P450 antibodies revealed that Irgasan DP 300 preferably induced CYP2B1/2 along with a slight increase in 3A. These results indicate that Irgasan DP 300 is a phenobarbital-type inducer. 4. In the absence of exogenous 5-aminolevulinic acid (ALA), slight increases in protoporphyrin IX (2.6-fold) and coproporphyrin III (1.3-fold) were observed in the Irgasan DP 300-treated cultures. In contrast, when 75 microM ALA was present, Irgasan DP 300 (250 microM) caused an extensive accumulation of uroporphyrin I (13-fold). 5. Irgasan DP 300 inhibited rat hepatic uroporphyrinogen III synthase in vitro. 6. These results indicate that Irgasan DP 300 produced accumulation of hydroxymethylbilane in rat hepatocytes by inhibiting uroporphyrinogen III synthase, and consequently an accumulation of uroporphyrin I.

Comparative toxicity of polychlorinated biphenyls to Japanese quail (Coturnix c. japonica) and American kestrels (Falco sparverius)

Polychlorinated biphenyls (PCBs) and related halogenated hydrocarbons bioaccumulate to high concentrations in top predators, such as raptorial birds, yet little is known of PCB toxicity to such species. This study explored several aspects of both the acute and chronic response of American kestrels (Falco sparverius) to three purified PCB congeners and a commercial mixture, Aroclor 1254, and compared the response to that of the Japanese quail (Coturnix c. japonica), a more studied species known to be PCB sensitive. In one experiment, adult female birds were given single oral doses of either Aroclor 1254, 3,3',4,4'-TCB (PCB 77, IUPAC nomenclature), 3,3',4,4',5-PCB (PCB 126) or 2,2',4,4',5,5'-HCB (PCB 153) and sacrificed after 5 d. In kestrels, neither the pure compounds nor the mixture affected hepatic or renal porphyrin levels. There was slight but significant hepatic and renal ethoxyresorufin O-deethylase (EROD) induction in birds dosed with PCBs 77 and 126. A cytochrome P-4501A (CYP1A) cross-reactive protein was detected in liver and kidney of kestrels given PCBs 77 and 126, but not in Aroclor 1254-dosed birds. In quail, an acute dose of Aroclor 1254 caused significant liver weight increases, hepatic and renal EROD and aminopyrine n-demethylase (APND) induction, and dose-related hepatic and renal porphyria. Quail treated with PCB 126 developed hepatic and renal porphyria; EROD and APND were also induced. Administration of PCB 77 caused only slight induction of hepatic EROD activity. PCB 153 caused some hepatic and renal porphyria and induced EROD to the same degree as PCB 126. A hepatic CYP1A cross-reactive protein was induced about 200-fold in all individual quail that exhibited significant EROD induction and was also induced in kidney of 1 quail given Aroclor 1254. A second experiment examined chronic exposure to Aroclor 1254 by feeding adult females of both species a daily dose of 7 mg/kg/d for 4-, 8-, and 12-wk periods. There were no effects on hepatic porphyrins in kestrels. APND and aldrin epoxidase (AE) were induced; EROD was not induced, although a hepatic CYP1A-like protein was detected in 1 kestrel dosed for 12 wk. Chronic exposure of quail to Aroclor 1254 caused highly significant increases in mean hepatic porphyrin levels and in activity of EROD, APND, and 4-chlorobiphenyl hydroxylase; a CYP1A-like protein was also induced about 200-fold. In both studies, Aroclor 1254 residues accumulated in tissues of both species, but there was no significant relationship between residue levels and effects. In conclusion, adult American kestrels were relatively insensitive to the effects of PCBs, from both acute and chronic exposure, on hepatic and renal porphyrin levels. Although concentrations of a CYP1A-like protein were increased in some kestrels given PCBs, EROD activity was only marginally increased, suggesting that catalytic activity of this protein differed among the two species.

Toxicological consequences of Aroclor 1254 ingestion by female rhesus (Macaca mulatta) monkeys. Part 1B. Prebreeding phase: clinical and analytical laboratory findings

A group of 80 menstruating rhesus (Macaca mulatta) monkeys, with an average estimated age of 11.1 +/- 4.1 yr SD were first randomly allocated to four similar test rooms (20 monkeys/room), and then randomly allocated to one of five dose groups (four females/dose group/room). Each day, the monkeys self-ingested capsules containing doses of 0, 5, 20, 40 or 80 micrograms Aroclor 1254/kg body weight. After 25 months of daily dosing, approximately 90% of the treated females attained a qualitative pharmacokinetic steady state with respect to the concentration of polychlorinated biphenyl (PCB) in their adipose tissue. Subsequently, oestrogen and progesterone concentrations in serum were determined for one complete oestrous cycle and various immunological tests were conducted, while the monkeys continued to receive their daily dose of PCB. During the prebreeding phase of the study, blood for clinical and analytical monitoring including haematology, serum biochemistry, serum hydrocortisone, serum proteins (alpha 1, alpha 2, beta and gamma-globulins), serum immunoglobulins (A, G and M) and thyroid variables (thyroxine/triiodothyronine (T3) uptake ratio, percentage T3 uptake and free thyroxine index), were obtained monthly, as were specimens to ascertain the concentration of PCB in the blood, adipose tissue and faeces. Major findings among treated monkeys included the following: changes in haematology (decreased erythrocyte count, haematocrit, reticulocyte count, and mean platelet volume), serum biochemistry (decreased cholesterol and total bilirubin), immunotoxicity (decreased antibody production to sheep red blood cells and alterations in the percentage of T helper and T suppressor cells) and pathology (the number of regions of sebaceous gland lobules per unit of histological length was significantly reduced). These effects were observed at PCB doses lower than those previously reported for non-human primates.

Comparative effects of the polychlorinated biphenyl mixture, aroclor 1242, on porphyrin and xenobiotic metabolism in kidney of japanese quail and rat

1. Aroclor 1242 (500 mg/kg, p.o.) produced a marked increase in porphyrin content of quail kidney (1800-fold), and of rat kidney but to a lesser extent (6-fold). 2. delta-Aminolevulinic acid synthetase activity was increased 12-fold in quail kidney but was unchanged in rat kidney following Aroclor 1242 treatment. 3. Uroporphyrinogen decarboxylase activity was significantly inhibited in quail kidney but not in rat kidney. 4. Renal ethoxyresorufin O-deethylase activity was induced in rat and quail whereas renal ethoxycoumarin O-deethylase and glutathione S-transferase activities were induced only in rats by Aroclor 1242.

Effects of polychlorinated biphenyls on cytochrome P450 induction in the chick embryo hepatocyte culture

The effects of pure synthetic polychlorinated biphenyl (PCB) congeners on the induction of cytochrome P450 and associated activities were examined in cultured chick embryo hepatocytes. Dose-response effects for the induction of total cytochrome P450 ethoxyresorufin-O-deethylase (EROD) activity, and benzphetamine demethylase (BPDM) activity were studied using 10 selected tetra- to hexachlorinated PCB congeners. These studies revealed that PCBs caused effects in the chick hepatocyte culture different from previously observed effects in rat liver. Based on their effects in chick hepatocytes, the PCBs could be categorized into two groups. The first group (consisting of 3,3',4,4'-PCB, 3,3',4,4',5-PCB, 3,3',4,4',5,5'-PCB, 2',3,3',4,5-PCB, 2,3,3',4,4',5'-PCB, and 2,3,4,4',5-PCB) induced total cytochrome P450 2.4- to 2.9-fold and EROD activity from 1-2 pmol/min/mg protein to 162-247. There was marked variation in potency, but all these congeners had a maximal inducing dose above which cytochrome P450 concentrations and EROD activities declined. BPDM activities were increased only slightly (1.2- to 1.6-fold) at the maximal cytochrome P450 inducing dose. The second group of congeners (consisting of 2,2',4,5,5'-PCB. 2,2',4,4',5,5'-PCB, and 2,2',3,4,4',6-PCB) induced total cytochrome P450 concentrations 4.0-fold and BPDM activities 2.2- to 2.6-fold with greatest activity occurring at the highest doses which could be added (10-50 microM). However, EROD activities were also increased by these congeners to 60-112 pmol/min/mg protein with declining activities seen at the highest PCB doses (i.e., resembling EROD induction patterns of the first group). The EROD induction patterns with these latter PCB congeners are noteworthy since these PCBs do not induce EROD activity in the rat. For both groups of PCB congeners, EROD induction was associated with increased accumulation of uroporphyrin in cultures exposed to exogenous 5-aminolevulinate. Studies investigating the reason for the depression of cytochrome P450 concentrations and/or EROD activities by high doses of the PCBs revealed that with the first group there was slightly decreased total protein synthesis, decreased total cell heme concentrations, and decreased accumulation of radiolabeled heme synthesized from 5-[14C]aminolevulinate. These changes might represent nonspecific toxic effects of the first group of PCBs. However, since these changes were not seen with the second group of PCBs, it is unlikely that either inhibition of heme synthesis or toxicity cause the depression of EROD activity with high PCB doses.

Urinary porphyrins in children exposed transplacentally to polyhalogenated aromatics in Taiwan

In 1979, there was a large (greater than 2,000 cases) outbreak of poisoning due to contaminated rice oil in central Taiwan. The causal agent was a mixture of thermally degraded polychlorinated biphenyls (PCBs), polychlorinated quaterphenyls, and polychlorinated dibenzofurans, which had become mixed with the oil during processing. Patients remained symptomatic for several years afterward, and the chemicals persisted in their tissue. Women who became pregnant had children with high perinatal mortality and a dysmorphic syndrome. We examined urines from 75 children born to exposed mothers after the oil was confiscated, 74 controls, and 12 sibs of the exposed children. Four of the transplacentally exposed children, 2 controls, and 1 sib had a type B hepatic porphyria (i.e., uroporphyrin greater than coproporphyrin); total porphyrin excretion was elevated in the exposed children as a group (95 vs. 81 micrograms/L); and 8 of the 75 exposed children and 2 controls had total urinary porphyrin concentrations of greater than 200 micrograms/L.

Role of inhibition of uroporphyrinogen decarboxylase in PCB-induced porphyria in mice

The oral administration of 3,4,5,3',4',5'-hexachlorobiphenyl for 3 weeks to mice caused a marked accumulation of porphyrins in the liver of C57BL/6 and C57Bl/10 mice but not in the liver of ddY mice. The time course of induction of delta-aminolevulinic acid synthetase (ALA-S), cytochrome P-450, and mixed function oxidases and inhibition of uroporphyrinogen decarboxylase (URO-D) in the liver of C57BL/6 mice and ddY mice fed a diet containing 500 ppm of a commercial PCB (Kanechlor-500) were investigated to clarify the sole factor in inducing porphyria. The activity of URO-D in the liver of C57BL/6 mice was depressed approximately 80% at 3 weeks when a large amount of uroporphyrin accumulated. Male ddY mice showed only a slight increase in uroporphyrin accumulation in the liver and a moderate decrease of URO-D activity even at the 10th week. ALA-S, cytochrome P-450, and mixed function oxidases were induced in both strains of mice, although the magnitude of these inductions in C57BL/6 mice was greater than that in ddY mice. No differences were detected between the two strains in the content and gas chromatographic pattern of PCB remaining in liver cytosol (6 weeks). In addition there was no relationship between the time of onset of porphyria and that of the maximal induction of drug-metabolizing function in C57BL/6 mice. These results indicate that the development of porphyria is causally related to the inhibition of URO-D rather than the induction of drug-metabolizing function. The hypothesis that porphyria first develops when the ratio of hepatic URO-D and ALA-S activities decreases to less than 1.0 is presented.

Pilot survey of urinary porphyrins from persons transiently exposed to a PCB transformer fire

In rats and humans chronically exposed to large amounts of PCB (polychlorinated biphenyls) and PCDF (polychlorinated dibenzofurans), the urinary excretion of uroporphyrin and coproporphyrin are altered. However, porphyrin excretion in humans after acute transient low level exposure has not been evaluated. Following such an exposure in which bystanders and firefighters were in contact with smoke from a PCB transformer fire, we surveyed 90 self-referred individuals by questionnaire and by determining single 24 hour urinary excretion of uroporphyrin and coproporphyrin 2-4 weeks after the fire. Questionnaire variables that assessed exposure were not associated with the magnitude of either uroporphyrin or coproporphyrin excretion. Uroporphyrin excretion was slightly elevated in nine subjects (range 66-106 micrograms/24 hours, normal less than 60), which is much less than in clinical cases of porphyria cutanea tarda. Uroporphyrin excretion was inversely correlated with coproporphyrin excretion (r = -0.3844, p = 0.0002). For 5 subjects (3 with elevated initial uroporphyrin excretion) retested at 3-4 weeks after the fire, all 5 showed increases in uroporphyrin and decreases in coproporphyrin excretion when compared to initial determinations. These two reciprocal relationships would be the expected result from inhibition of uroporphyrinogen decarboxylase, a known experimental effect of PCB and PCDF in mice. Overall, urinary porphyrin excretions were not altered or sensitive measures of exposure.

Exposure to toxic agents: the heme biosynthetic pathway and hemoproteins as indicator

The heme biosynthetic pathway is closely controlled by levels of the end product of the pathway, namely, heme, and porphyrins are normally formed in only trace amounts. When control mechanisms are disturbed by xenobiotics, porphyrins accumulate and serve as a signal of the interaction between a xenobiotic and the heme biosynthetic pathway. For example, an increase in erythrocyte protoporphyrin is a useful measurement for early detection of exposure to lead and porphyrinuria was an early manifestation of a hexachlorobenzene-induced porphyria in Turkey. In recent years a variety of additional xenobiotics has been shown to interact with the heme biosynthetic pathway, namely, halogenated aromatic hydrocarbons, pesticides, sulfides, and a variety of metals. Moreover, different xenobiotics (e.g., dihydropyridines and compounds containing unsaturated carbon-carbon bonds) interact with the prosthetic heme of cytochrome P-450 forming novel N-alkylporphyrins.

Polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs): biochemistry, toxicology, and mechanism of action

Polychlorinated and polybrominated biphenyls are industrial chemical mixtures which have been implicated in numerous human poisonings in Taiwan and Japan (PCBs) and Michigan (PBBs). Moreover, these polyhalogenated biphenyls have been widely detected in the environment including the air, water, fish, wildlife, human adipose tissue, and blood and breast milk. A major problem associated with the analysis and toxicology of this group of chemicals is their chemical complexity (e.g., there are 209 possible PCB isomers and congeners) and the remarkable effects of structure on activity. This article will discuss the effects of structure on the biologic and toxic effects of individual PCB and PBB congeners as well as reconstituted mixtures. The results clearly show that like "dioxin" (or 2,3,7,8-TCDD), the PCBs and PBBs elicit their effects through a cytosolic receptor protein which preferentially binds with the toxins which are approximate isostereomers of 2,3,7,8-TCDD. The evidence for this mechanism of action will be discussed in detail.

Effects of polychlorinated biphenyl compounds, 2,3,7,8-tetrachlorodibenzo-p-dioxin, phenobarbital and iron on hepatic uroporphyrinogen decarboxylase. Implications for the pathogenesis of porphyria

Treatment of cultured chick embryo hepatocytes with phenobarbital, polychlorinated biphenyl compounds and 2,3,7,8-tetrachlorodibenzo-p-dioxin resulted in increased delta-aminolaevulinate synthase and decreased uroporphyrinogen decarboxylase activities and porphyrin accumulation; uroporphyrin and heptacarboxyporphyrin predominated. Iron had no effect on these changes. Simultaneous treatment of cultures with dioxin and phenobarbital produced a synergistic response in delta-aminolaevulinate synthase induction, uroporphyrinogen decarboxylase inhibition and porphyrin accumulation. These data suggest that an inhibitor of uroporphyrinogen decarboxylase may be generated in the liver from polychlorinated biphenyl compounds or dioxin by metabolic activation. Additionally these findings bear on the postulated role of these and related chemicals in determining the low levels of uroporphyrinogen decarboxylase activity in porphyria cutanea tarda patients.

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.

Induction of porphyria in the rat by chronic versus acute exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin

Chronic oral administration of 1 microgram . kg-1 . week-1 of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to female rats for 16 weeks resulted in hepatic porphyria. In contrast, administration of single oral doses as high as 30 micrograms/kg did not produce porphyria, either acutely or 16 weeks later. Activities of hepatic drug-metabolizing enzymes [aryl hydrocarbon hydroxylase (AHH) and glucuronyl transferase] were increased by chronic oral doses of TCDD as low as 0.01 microgram . kg-1 . week-1. When animals were dosed with TCDD chronically and then allowed to recover for 6 months, AHH and glucuronyl transferase activities returned toward normal (98 and 86% recovery). However, animals showed only partial recovery from TCDD-induced porphyria. Hepatic porphyrin levels did decrease during this period, but urinary porphyrins and the rate-limiting enzyme in porphyrin synthesis, delta-aminolevulinic acid synthetase, remained maximally elevated during the 6-month recovery period. It is concluded that single doses of TCDD do not produce porphyria in the rat, but that TCDD is porphyrogenic when given chronically. Moreover, when TCDD administration is stopped, recovery from the porphyrogenic effects of TCDD is very slow and does not correlate with the biological half-life of TCDD in the rat.

Subchronic dermal toxicity study of trichlorobenzene in the rabbit

Groups of five male and five female New Zealand albino rabbits were treated by skin application with either 0 (distilled water control), 30, 150 or 450 mg/kg undiluted trichlorobenzene (ICB) for 5 days/week for four weeks. No treatment related systemic effects were observed at any of the treatment levels when body weight, clinical chemistry and organ weight parameters were measured. Systemic effects due to dermal application of TCB were present only in rabbits given 450 mg/kg/day. These effects included a slight but statistically significant increase in the urinary coproporphyrin excretion in males and slight pallor of the liver at gross necropsy in both sexes. Localized effects at the site of application were present in all treated rabbits. These effects were characteristic of the response to dermal irritation. Grossly, the fur was matted by a fine white bran-like scales with variable degrees of erythema, fissures, erosions and ulcers. Histopathologically, there was inflammation and thickening of the epidermis. The size of the affected area varied directly with the dose level. Based on the results of the study, it was concluded that a dose level of 450 mg/kg/day of TCB applied dermally to rabbits induced slight systemic toxicity. The no-observable effect level for systemic toxicity was 150 mg/kg/day when TCB was applied to the skin of male and female rabbits over the course of 30 days.

Effect of parathion, malathion, endosulfan and chlordane on porphyrin accumulation and ALA-synthetase in chick embryo liver

In the present study we investigated the porphyrinogenic ability of 4 pesticides: chlordane, endosulfan, parathion and malathion, all of which are widely used in agriculture. In order to determine whether they affect the heme biosynthetic pathway we studied, in 17-day old chick embryo liver "in ovo", their effects on the amount of porphyrins and on the activity of delta-ALA synthetase (ALA-S), the first and rate limiting enzyme of this pathway. All of them induced hepatic porphyrin accumulation to a different extent compared with dimethylsulfoxide (DMSO) controls. Parathion as well as endosulfan promoted remarkable increases, chlordane raised porphyrin level in a lower degree and malathion slightly modified it. However, the accumulation observed with malathion was markedly enhanced if the period of incubation was extended to 48 h and, even more, if a second dose was injected during these 48 h. When ALA-S activity was analyzed in the chick embryos treated with parathion or endosulfan no alteration could be found in spite of producing noticeable accumulation of porphyrins. In contrast, chlordane promoted a statistically significant elevation of ALA-S as well as malathion which produced the highest induction observed. These results show that not only organochlorinated but also organophosphorous pesticides affect heme metabolism and that induction of ALA-S and porphyrin accumulation are not parallel.

Subchronic toxicity study of 1,2,4-trichlorobenzene in the rat, rabbit and beagle dog

Male rats, rabbits and dogs were exposed to 0, 30 or 100 ppm of 1,2,4-trichlorobenzene (TCB) for 7 hours/day, 5 day/week for 30 exposures in 44 days. In all 3 species, there were no significant effects on body weight gain, hematologic and serum biochemical tests or gross and histopathologic appearance of tissues. At 100 ppm TCB, both rats and dogs had increased liver weights, and the rats also had increased relative kidney weight at this higher exposure level. Urinary excretion of porphyrins were increased in rats exposed to 30 or 100 ppm TCB, most likely as a result of hepatic induction by TCB. In view of the reversibility of this porphyrin induction noted in a companion study, and the absence of other indications of discernible toxicity, this increased urinary excretion of porphyrins is best considered more of a compound-specific physiologic effect rather than a toxic effect.

High-performance liquid chromatographic determination of protoporphyrin and zinc protoporphyrin in blood

Zinc protoporphyrin and protoporphyrin free acid in blood were determined by high-performance liquid chromatography on a C18 column. Results for 63 human blood samples obtained through a lead poisoning detection program compared favorably with the widely-used ethyl acetate--acetic acid extraction determination. Blood from 16 rats which had been maintained on water heavily spiked with chloroform or bromodichloromethane and blood from a lead-poisoned cow were examined by this procedure.

World PCBs map: storage and effects in man and his biologic environment in the 1970s

PCB residues are found in biota all over the world. A biologic magnification of PCBs has been demonstrated in the food chain: plankton-fish-fish eating birds. A world map of the PCBs residues in biota and some of their biologic effects are given in this study. The biologic effects of PCBs are varied and may generally be explained by the induction or inhibition of the activity of a large number of enzymes, which upsets quantitatively, normal biochemical processes. Harm to reproduction, growth, development, defense systems, tissues, and organs appeared in susceptible organisms as a result of such changes or as a chain reaction to heterostases. The adverse health effects, observed in persons occupationally exposed and in those accidentally poisoned, point to the risk for the general population of an ever-increasing environmental pollution by PCBs. There is need for an integrated approach, consisting of epidemiologic studies on high risk groups in the general population and in persons occupationally exposed, as well as periodic assessment of PCB residues in man, his food, and feed supplies.

Brominated benzene induction of hepatic porphyria

Unlike the highly porphyrinogenic fungicide hexachlorobenzene, hexabromobenzene was a poor inducer of porphyria. Similarly, 1,2-dibromobenzene and 1,2,4-tribromobenzene, while causing small increases in hepatic porphyrins, did not increase ALA synthetase or the urinary excretion of porphobilinogen (PBG), aminolevulinic acid (ALA) or porphyrins.

Short term effects of Clophen A 50 and of dichlorobiphenyl in rats

In short term experiments, rats were treated with single oral doses of the polychlorinated biphenyls (PCB's), Clophen A 50 (high chlorinated compound) and dichlorobiphenyl (low chlorinated compound). Clophen A 50 treatment resulted in a marked increase in liver weight and in the activities of GPT, GOT and G1DH in rat serum at 1000 mg/kg similar effects were observed, but to a lesser degree. The levels of the serum lipids, cholesterol and triglycerides were significantly elevated at both dose levels and they remained elevated up to seven days. In contrast, one single oral dose of 1000 mg of dichlorobiphenyl per kg did not cause significant changes in the above mentioned parameters. Histological examination of the liver showed irregularly disseminated droplets of fat in both experiments. These results indicate that Clophen A 50 causes liver damage and alters the lipid metabolism of rats, whereas the low chlorinated dichlorobiphenyl does not exert such effects.

Studies on the cellular toxicity of polychlorinated biphenyls (PCBs). I. Effect of PCBs on microsomal enzymes and on synthesis and turnover of microsomal and cytoplasmic lipids of rat liver- a morphological and biochemical study

The acute effects of the PCB (polychlorinated biphenyls) mixture (Aroclor 1254) on microsomal enzymes and on synthesis and turnover of microsomal and cytoplasmic lipids of rat liver were investigated. Six daily i.p. injections of 25 and 50 mg PCB/kg body weight resulted in increased liver weight and liver to body weight ratios. When compared to controls PCB treatment resulted in a six-fold increase in amount of cytochrome P-450. Activities of NADPH-cytochrome c reductase, ethylmorphine demethylase and inosine diphosphatase were increased whereas glucose-6-phosphatase values were decreased by PCB exposure. Analysis of liver homogenate and microsomal fraction revealed an increase in lipid in PCB-exposed animals. Phospholipids, cholesterol and triglyceride were significantly increased after PCB exposure; however, the greatest percentage increase was seen in the triglyceride pool. The finding of an increase in microsomal triglyceride to phospholipid ratios with exposure to PCB is suggestive of an increase in membrane-enclosed lipid (liposomes). Studies with labelled glycerol indicated that the PCB-induced fatty liver resulted from increased half life but not increased synthesis of liver lipid moieties. The rate of incorporation of leucine into microsomal membrane and albumin was somewhat enhanced in rats exposed to PCB indicative of increased protein synthesis. Morphological studies showed increased occurrence of lipid material, both in cytoplasmic droplets and within rough and smooth-surfaced endoplasmic reticulum. Proliferation of smooth endoplasmic reticulum and flattened Golgi cisternae with no secretion granules containing lipoprotein particles characterized the liver from animals exposed for 6 days. The increase in lipid within membranes of the endoplasmic reticulum together with the flattened Golgi lacking typical secretory vesicles indicates a defect in transport of lipoproteins from the endoplasmic reticulum to the Golgi apparatus and may be the cause of the PCB-induced fatty liver.