J. R. Allen

Reproductive dysfunction in rhesus monkeys exposed to low levels of polychlorinated biphenyls (Aroclor 1248)

Abstract Eighteen female and four male adult rhesus monkeys were fed the polychlorinated biphenyl (PCB) Aroclor 1248 at levels of either 2·5 or 5·0 ppm in the diet. These levels are equal to and 50% of the concentration allowed in certain foods destined for human consumption. After consuming these diets for 2 months, some of the females developed acne, alopecia, erythema and swelling of the eyelids, and by 6 months all females exhibited these changes to some degree. Modifications in serum lipids developed gradually, with a trend towards hypocholesterolaemia, hypolipidaemia and decreased serum triglycerides. In addition there was a shift in the plasma albumin/globulin ratio and an increase in serum glutamic-pyruvic transaminase activity. Analysis of subcutaneous fat showed an accumulation of the PCB isomers in the adipose tissue. The concentrations in this tissue reached a plateau, after which only slight variations were observed. Within 4 months, menstrual cycles were altered menostaxis and menorrhagia occurred frequently and at times amenorrhoea was apparent. The ability of the animals to maintain pregnancy was impaired, as indicated by frequent resorptions and abortions. When infants were born they were small, and the transplacental movement of PCBs was evident from analyses of skin biopsies of neonates and of autopsy tissue from one stillborn. Moreover, additional accumulation of PCBs occurred in infants during breast feeding. All males fed 5·0 ppm PCB exhibited only slight periorbital oedema and erythema after 14 months on the diet and showed no alterations in their breeding capacities. The data presented indicate that long-term, low-level exposure of female non-human primates to PCBs can affect many important biological parameters.

REPRODUCTIVE EFFECTS OF HALOGENATED AROMATIC HYDROCARBONS ON NONHUMAN PRIMATES

During the past several years experiments have been conducted in this laboratory to determine the toxicologic effects in animals exposed to three halogenated hydrocarbons-2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs). TCDD and PCBs are considered to be worldwide environmental contaminants. PBBs have caused major environmental problems in the state of Michigan. The health implications of these compounds are further complicated by their extremely slow biodegradation and their ability to accumulate in body tissues and remain there for an indefinite period. As a result of their environmental and public health significance, a large amount of literature has been published on TCDD and PCB intoxication in humans and lower animals. There is also considerable research in progress to further clarify the toxicologic effects of the PBBs. However, there is a dearth of information on the effects of these halogenated hydrocarbons on reproduction in humans and closely related species, particularly when the exposure to these compounds is at low levels and occurs over an extended period. The rhesus monkey is a suitable animal model with which to study the effects of exposure to halogenated hydrocarbons. Many of the toxicologic signs produced by these halogenated hydrocarbons are similar to those observed in humans. Thus, the data obtained from research conducted on the nonhuman primate are helpful in postulating the injurious effects that may arise in the human population following exposure to these compounds. I n the presently reported research, the three compounds were evaluated for their toxicologic effects on nonhuman primates. Attempts have been made to simulate the levels to which humans may be exposed. Data are presented which indicate that low-level, long-term exposure to these compounds gives rise to reproductive abnormalities in the adult primate as well as fetal and neonatal toxicity.

Morphological changes in monkeys consuming a diet containing low levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin

Abstract Female rhesus monkeys given a diet containing 500 ppt (t = 1012) 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for 9 months became anaemic within 6 months and pancytopenic after 9 months of exposure. The marked thrombocytopenia was associated with widespread haemorrhage. Death occurred in five of the eight animals between months 7 and 12 of the experiment at total exposure levels of 2–3 μg TCDD/kg body weight. At autopsy, in addition to the extensive haemorrhage, there was a distinct hypocellularity of the bone marrow and lymph nodes. Hypertrophy, hyperplasia and metaplasia of the epithelium in the bronchial tree, bile ducts, pancreatic ducts, salivary-gland ducts and palpebral conjunctivae were observed. Squamous metaplasia and keratinization of the sebaceous glands and hair follicles were present in the skin. Death was attributed to complications from the severe pancytopenia.

Tissue distribution, excretion and biological effects of [14C]tetrachlorodibenzo-p-dioxin in rats.

Abstract When Sprague-Dawley rats weighing 200 g were intubated intragastrically with 14C-labelled 2,3,7,8-tetrachlorodibenzo-p-dioxin in a dose of 50 μg/kg body weight, 50% of the animals died within 25 days. Over 56% of the radioactivity was eliminated, mainly by the alimentary route, during the initial 21 days, 25% being accounted for during the first 3 days. The total amount of radioactivity in the urine was 4·5% of the total dose, the highest daily levels being excreted toward the end of the experiment. A large percentage of the radioactivity remaining in the body was localized in the liver and of this, over 90% was within the microsomal fraction. The major morphological changes in these rats were a marked liver hypertrophy and thymic regression.

Tissue distribution and excretion of tritiated tetrachlorodibenzo-p-dioxin in non-human primates and rats

Tritiated 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was given to adult and infant rhesus monkeys and to rats to determine the distribution of this compound and to compare the tissue localization of the compound in the two species. Excretion, both daily and total, was similar in all three groups of animals, as was total tritium recovery. However, the concentration and total level of tritium in most tissues differed significantly between species. In the rat, retention in the liver accounted for over 40% of the administered dose, while this level was less than 10% in the livers of the monkeys. In contrast, a large percentage of the dose was located in the monkey in tissues with a high lipid content, particularly the skin, muscle and fat. In the rat, these tissues had much lower levels of TCDD.

Residual effects of short-term, low-level exposure of nonhuman primates to polychlorinated biphenyls☆

Abstract Six adult female rhesus monkeys were fed the polychlorinated biphenyl (PCB) Aroclor 1248 at a level of 25 ppm for 2 months. Facial edema, alopecia, and acne developed within 1 month, and one animal died as a result of PCB intoxication 2 months after removal from the experimental diet. In addition to the above changes, this animal had anemia, hypoproteinemia, severe hypertrophic, hyperplastic gastritis, and bone marrow hypoplasia. Polychlorinated biphenyl concentrations in samples of subcutaneous adipose tissue obtained from all experimental animals averaged 127 μg/g fat at the time the experimental diet was discontinued. Eight months later the PCB content of the adipose tissue had decreased to 34 μg/g fat. However, the five surviving animals continued to show clinical signs and lesions of PCB intoxication. An infant born to one of these PCB-fed females was small and had over 25 μg PCB/g of adrenal and adipose tissue. These data attest to the toxicity of short-term, low-level exposure to PCBs in nonhuman primates and to the persistence of the toxic effects long after exposure has been eliminated.

Residual effects of polychlorinated biphenyls on adult nonhuman primates and their offspring

After 18 mo of consuming a diet containing 2.5 and 5.0 ppm PCB (Aroclor 1248), during which they and their offspring experienced marked alterations in physical status, female rhesus monkeys were placed on a control diet for 1 yr. During this year there was a decided improvement in their general body health and reproductive capabilities. Infants born to these animals were small at birth and during their postnatal life developed signs of PCB intoxication similar to those observed in their siblings born during the period of PCB exposure. These data indicate that the residual effects of low-level ingestion of PCBs by nonhuman primates persist for over 1 yr after discontinuation of exposure. There are also indications that the fetal and neonatal monkeys born to PCB-exposed mothers are more severely affected for a longer period than are the adult female monkeys.

Right ventricular hypertrophy in monocrotaline pyrrole treated rats

Abstract Single, tail-vein injections of 2–4 mg/kg body weight of monocrotaline pyrrole produced an endothelial lesion in the cells lining the capillaries and arterioles of the rat lung. Within 4 weeks, numerous pulmonary vessels became partially or completely occluded by fibrin and platelet thrombi, by enlargement of the endothelium, and by hypertrophy of smooth muscle cells in the tunica media. Impairment of the pulmonary blood flow led to tissue hypoxia which was reflected by an increase in hemoglobin, hematocrit, and erythrocyte count values. In addition, there was a fourfold increase in peak systolic blood pressure within the lumen of the right ventricle. This hypertension was progressive and caused an increase in the workload of the right heart. Right ventricular hypertrophy developed gradually over 2–3 weeks so that by 4 weeks the right side of the heart weighed almost 3 times that of the controls. It is suggested that monocrotaline pyrrole injected animals provide a readily reproducible model for experimental cardiac hypertrophy which mimics the gradual onset of cardiac disease observed clinically in man.

Responses of rats exposed to polychlorinated biphenyls for fifty-two weeks I. Comparison of tissue levels of PCB and biological changes

Male Sprague-Dawley rats were fed a diet containing mixtures of polychlorinated biphenyls (PCB) isomers (Aroclor 1248, 1254 and 1262) at a concentration of 100 ppm in the diet for 52 weeks. During the subsequent 13 weeks the rats were placed on a control diet. Throughout the course of the experiment the animals ate well, were healthy in appearance and gained weight as rapidly as the control animals. Their hemograms were normal. In spite of the gross normalcy of these animals throughout the 52-week experimental period, clinical and morphologic examinations revealed distinct alterations. There was a decided increase in their total serum lipids and cholesterol and a transient increase in triglycerides accompanied by distinct morphological changes in the liver. Generalized liver hypertrophy and focal areas of hepatocellular degeneration were followed by a wide spectrum of repair processes. The tissue levels of PCB were greater in the animals receiving the higher chlorine mixtures. High levels persisted in these tissues even after the PCBs had been discontinued.

Modifications of pyrrolizidine alkaloid intoxication resulting from altered hepatic microsomal enzymes

Abstract Levels of hepatic microsomal activity are instrumental in determining the toxicity of the pyrrolizidine alkaloid, monocrotaline. Following the stimulation of microsomal enzymes with phenobarbital prior to the administration of monocrotaline, rats gained less weight, developed more severe lung lesions at an earlier time, and died more rapidly than those that received only monocrotaline. However, in rats pretreated with the enzyme inhibitor chloramphenicol, there was an absence of mortality, the growth rate was unaffected and the lesions were less severe than in rats given monocrotaline or in those pretreated with phenobarbital and subsequently given monocrotaline. The acute toxic effects produced by the metabolic pyrroles may be suppressed by the use of inhibiting agents such as chloramphenicol, thereby permitting the development of more chronic lesions such as megalohepatocytosis in monocrotaline-intoxicated animals.