CADMIUM NEOPLASIA: TESTICULAR ATROPHY AND LEYDIG CELL HYPERPLASIA AND NEOPLASIA IN RATS AND MICE FOLLOWING THE SUBCUTANEOUS INJECTION OF CADMIUM SALTS

Significance of Leydig Cell Neoplasia in Rats Fed Lactitol or Lactose

Lactitol is a disaccharide sugar alcohol (polyol) which is derived from lactose by catalytic hydrogenation and which may be used as a noncariogenic, reduced calorie sugar substitute in different foods. In the context of the safety evaluation of lactitol, a chronic carcinogenicity/toxicity study was conducted in a Wistar-derived strain of rats. In addition to effects that occur commonly in rats fed high doses of polyols, an increased incidence of Leydig cell tumors was observed in rats fed a diet with 10% lactitol for their lifetime. A comparison group receiving a diet with 20% lactose exhibited the same effect. At the 5% dose level of lactitol, no testicular changes were seen. Although lactitol is not genotoxic in standard in vitro tests and was also not associated with tumor formation in female rats and mice of either sex, it was necessary to assess the relevance of the testicular neoplastic growth for human safety. A comparative evaluation of the spontaneous and chemically induced formation of Leydig cell tumors in rats and humans demonstrates that the spontaneous occurrence is extremely low in humans but rather high in rats. Chemical agents or experimental conditions that in rats are associated with interstitial cell hyperplasia or neoplasia have not been associated with similar effects in humans. This is also true for lactose which, in Western countries, is consumed regularly and in substantial amounts with dairy products. Since lactitol is essentially not hydrolyzed in the small intestine, it gains access to the metabolism only after fermentation by the intestinal flora. It is therefore reasonable to assume that the testicular effects of lactitol and lactose were mediated by changes in the digestive tract such as by the known increase of calcium absorption which occurs in lactitol- and lactose-fed rats but not in humans or by effects of these compounds on the enterohepatic cycling of steroid hormones. Although these mechanisms are not yet elucidated, the available data on Leydig cell tumors indicate that the effects seen in male rats are not relevant to humans. The major lines of evidence supporting the human safety of lactitol and lactose are: (1) the lack of genotoxicity of lactitol, (2) the rat specificity of the testicular effects of lactose and lactitol, (3) the long history of safe consumption of lactose in humans, (4) the insensitivity of the human Leydig cells to agents and conditions that are known to cause neoplastic growth of Leydig cells in rats, (5) the generally very low spontaneous incidence of Leydig cell tumors in the human population, and (6) the absence of any epidemiological evidence establishing a link between nutritional factors and the occurrence of Leydig cell tumors in humans.

Cadmium-induced testicular injury

Cadmium (Cd) is an environmental toxicant and an endocrine disruptor in humans and rodents. Several organs (e.g., kidney, liver) are affected by Cd and recent studies have illustrated that the testis is exceedingly sensitive to Cd toxicity. More important, Cd and other toxicants, such as heavy metals (e.g., lead, mercury) and estrogenic-based compounds (e.g., bisphenols) may account for the recent declining fertility in men among developed countries by reducing sperm count and testis function. In this review, we critically discuss recent data in the field that have demonstrated the Cd-induced toxicity to the testis is probably the result of interactions of a complex network of causes. This is likely to involve the disruption of the blood-testis barrier (BTB) via specific signal transduction pathways and signaling molecules, such as p38 mitogen-activated protein kinase (MAPK). We also summarize current studies on factors that confer and/or regulate the testis sensitivity to Cd, such as Cd transporters and metallothioneins, the impact of Cd on the testis as an endocrine disruptor and oxidative stress inducer, and how it may disrupt the Zn(2+) and/or Ca(2+) mediated cellular events. While much work is needed before a unified mechanistic pathway of Cd-induced testicular toxicity emerges, recent studies have helped to identify some of the likely mechanisms and/or events that take place during Cd-induced testis injury. Furthermore, some of the recent studies have shed lights on potential therapeutic or preventive approaches that can be developed in future studies by blocking or minimizing the destructive effects of Cd to testicular function in men.

Review of cadmium transfers from soil to humans and its health effects and Jamaican environment

Concerns about the effects of cadmium on human health have led to numerous guidelines and regulations limiting its concentrations in soils and food and allowable human intakes. These have socio-economic consequences in terms of land use and the marketing of food. The bauxite soils in Jamaica, which are both aluminium ores and agricultural soils contain orders of magnitude higher than world normal concentrations of cadmium resulting in elevated Cd concentrations in several foodstuffs and significant transfers to humans, which would seem to represent a risk factor for increased mortality and/or morbidity in the local populations. But, as in Shipham and other examples, there is no evidence of cadmium-related human distress. Macro-indicators like life expectancy and median ages of death do not show cadmium related geographical distributions. The present review focuses on the soils and foods and illnesses of high incidence especially cancers and renal disease that have been traditionally associated with cadmium. In view of the remarkable concentrations of cadmium involved in Jamaica, and often contradictory reports in the literature, it appears that much remains to be learned about certain details of cadmium toxicity.

Cadmium-induced cancers in animals and in humans

Discovered in the early 1800s, the use of cadmium and various cadmium salts started to become industrially important near the close of the 19th century, rapidly thereafter began to flourish, yet has diminished more recently. Most cadmium used in the United States is a byproduct from the smelting of zinc, lead, or copper ores, and is used to manufacture batteries. Carcinogenic activity of cadmium was discovered first in animals and only subsequently in humans. Cadmium and cadmium compounds have been classified as known human carcinogens by the International Agency for Research on Cancer and the National Toxicology Program based on epidemiologic studies showing a causal association with lung cancer, and possibly prostate cancer, and studies in experimental animals, demonstrating that cadmium causes tumors at multiple tissue sites, by various routes of exposure, and in several species and strains. Epidemiologic studies published since these evaluations suggest that cadmium is also associated with cancers of the breast, kidney, pancreas, and urinary bladder. The basic metal cationic portion of cadmium is responsible for both toxic and carcinogenic activity, and the mechanism of carcinogenicity appears to be multifactorial. Available information about the carcinogenicity of cadmium and cadmium compounds is reviewed, evaluated, and discussed.

Perspectives on cadmium toxicity research

Since there are a plethora of studies on cadmium toxicity and poisoning in laboratory animals and humans, we have limited this review to studies that are relevant to human health issues by focusing on carcinogenicity, genotoxicity, circulatory disease, nephrotoxicity and life expectancy. Cadmium exposure has been established to induce cancer in various tissues of laboratory animals. Contrary to early findings of the lack of genotoxicity by cadmium, recent findings of mammalian cell culture studies have revealed genotoxic effects. Furthermore, cadmium exposure at relatively low doses induces circulatory diseases in laboratory animals. Despite such results of various cadmium toxicities in animal studies, data from human studies are lacking and insufficient to support the cause-effect relationship. Although cadmium is currently considered to be a human carcinogen by the International Agency for Research and Cancer, it is inappropriate to conclude that sufficient evidence on the carcinogenicity of cadmium in humans exists. It is also thought that epidemiological studies so far reported do not support the occurrence of cadmium-induced circulatory disease in humans. Since there are inconsistent reports on the relationship of cadmium exposure with the life expectancy of people living in cadmium-polluted areas, further studies are needed for clarification. It is also necessary to examine apparent discrepancies in result between humans and experimental animals. It has been established that long-term exposure to cadmium causes renal dysfunction in both humans and experimental animals, and whether there are any differences in the inducibility of metallothionein in the kidney warrants further study.

Rodent Leydig cell tumorigenesis: a review of the physiology, pathology, mechanisms, and relevance to humans

Leydig cells (LCs) are the cells of the testis that have as their primary function the production of testosterone. LCs are a common target of compounds tested in rodent carcinogenicity bioassays. The number of reviews on Leydig cell tumors (LCTs) has increased in recent years because of its common occurrence in rodent bioassays and the importance in assessing the relevance of this tumor type to humans. To date, there have been no comprehensive reviews to identify all the compounds that have been shown to induce LCTs in rodents or has any review systematically evaluated the epidemiology data to determine whether humans were at increased risk for developing LCTs from exposure to these agents. This review attempts to fill these deficiencies in the literature by comparing the cytology and ontogeny of the LC, as well as the endocrine and paracrine regulation of both normal and tumorigenic LCs. In addition, the pathology of LCTs in rodents and humans is compared, compounds that induce LC hyperplasia or tumors are enumerated, and the human relevance of chemical-induced LCTs is discussed. There are plausible mechanisms for the chemical induction of LCTs, as typified by agonists of estrogen, gonadotropin releasing hormone (GnRH), and dopamine receptors, androgen receptor antagonists, and inhibitors of 5alpha-reductase, testosterone biosynthesis, and aromatase. Most of these ultimately involve elevation in serum luteinizing hormone (LH) and/or LC responsiveness to LH as proximate mediators. It is expected that further work will uncover additional mechanisms by which LCTs may arise, especially the role of growth factors in modulating LC tumorigenesis. Regarding human relevance, the pathways for regulation of the hypothalamo-pituitary-testis (HPT) axis of rats and humans are similar, such that compounds that either decrease testosterone or estradiol levels or their recognition will increase LH levels. Hence, compounds that induce LCTs in rats by disruption of the HPT axis pose a risk to human health, except for possibly two classes of compounds (GnRH and dopamine agonists). Because GnRH and prolactin receptors are either not expressed or are expressed at very low levels in the testes in humans, the induction of LCTs in rats by GnRH and dopamine agonists would appear not to be relevant to humans; however, the potential relevance to humans of the remaining five pathways of LCT induction cannot be ruled out. Therefore, the central issue becomes what is the relative sensitivity between rat and human LCs in their response to increased LH levels; specifically, is the proliferative stimulus initiated by increased levels of LH attenuated, similar, or enhanced in human vs. rat LCs? There are several lines of evidence that suggest that human LCs are quantitatively less sensitive than rats in their proliferative response to LH, and hence in their sensitivity to chemically induced LCTs. This evidence includes the following: (1) the human incidence of LCTs is much lower than in rodents even when corrected for detection bias; (2) several comparative differences exist between rat and human LCs that may contribute, at least in part, to the greater susceptibility of the rat to both spontaneous and xenobiotic-induced LCTs; (3) endocrine disease states in man (such as androgen-insensitivity syndrome and familial male precocious puberty) underscore the marked comparative differences that exist between rats and man in the responsiveness of their LC's to proliferative stimuli; and (4) several human epidemiology studies are available on a number of compounds that induce LCTs in rats (1,3-butadiene, cadmium, ethanol, lactose, lead, nicotine) that demonstrate no association between human exposure to these compounds and induction of LC hyperplasia or adenomas. (ABSTRACT TRUNCATED)

CADMIUM NEOPLASIA: SARCOMATA AT THE SITE OF INJECTION OF CADMIUM SULPHATE IN RATS AND MICE

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Nutrition and prostate cancer

Epidemiologic evidence on the relation between nutrition and prostate cancer is reviewed. Little is known about the etiology of prostate cancer, despite its prominence as the leading cancer among men in the United States. Rational mechanisms for dietary influences on prostate carcinogenesis, including effects on production or metabolism of androgenic hormones, have been proposed, but because few suitable animal models have been developed, the laboratory literature on diet and prostate cancer is sparse. Despite strong ecologic data and largely consistent case-control and cohort data on dietary fat and prostate cancer, the role of this nutrient remains unclear. Few studies, to date, have adjusted the results for caloric intake, and no particular fat component has been consistently implicated. A notable finding is a strong positive association with intake of animal products, especially red meats, but this in itself does not specifically implicate fat. Epidemiologic investigations on vitamin A and carotenoids are divided almost equally between studies showing positive and inverse associations. The evidence from these studies for a protective effect of fruits and vegetables on prostate cancer, unlike many other cancer sites, is not convincing. The data on other dietary components that have been examined with regard to prostate cancer etiology (cadmium, zinc, vitamins C and D, beverages, and legumes) are too incomplete at this time to draw any inferences as to their importance. The evidence for anthropometric associations with prostate cancer is weak. Whereas a clear association with obesity has not been shown, a positive relationship to muscle mass, though not yet established conclusively, further suggests the importance of androgens in this cancer.

High frequency of metalworkers among patients with seminomatous tumors of the testis: a case-control study

Occupational analyses were conducted between 1971 and 1978 comparing 165 cases of testicular cancer in the Hannover region of Germany with 187 controls without neoplastic diseases admitted to the Hannover University Medical School during the same period. The results showed a significantly higher risk of metal workers developing seminomas and mixed seminomatous tumors compared to the controls (odds ratio 2.05; 1.17-3.58). There was a lack of risk for the nonseminomatous tumors as a whole group, and cases with a history of metal work may have a decreased risk for embryonal carcinomas. No definite single noxious substance responsible for the development of testicular tumors could be detected. In view of the results in animal experiments, cadmium and zinc are especially considered in the discussion.

Cadmium and prostate cancer

Prostatic cancer is a common and frequently lethal malignant disease. In the United States and other countries the incidence and mortality rate of prostate cancer continue to rise. Cancer of the prostate has an extremely complex etiology and appears dependent on a variety of factors, making linkage to a single factor very difficult to detect. Cadmium is a metallic toxin of great environmental and occupational concern. Cadmium exposure has been associated with human prostatic cancer in some, but not all, epidemiologic studies. Some studies indicate that tissue levels of cadmium in the human prostate correlate with malignant disease. Any association between cadmium and prostatic cancer has been controversial, in large part because of a previous lack of relevant animal models. However, several chronic studies in rats revealing a correlation between cadmium exposure and prostatic tumors have been published over the last several years. These include a study of oral cadmium exposure, a route extremely relevant to human exposure. Several of these chronic studies indicate a hormonal dependence of cadmium-induced prostate cancer. Other supportive work continues to accumulate, such as studies showing in vitro malignant transformation of prostatic epithelial cells with cadmium exposure. In addition, there are indications that the primary biologic tolerance system for cadmium (i.e., the metallothionein gene) may be only poorly active in the specific lobes of the rat prostate in which cadmium induces tumors. The induction in rats of prostate cancer by cadmium treatment clearly supports, but does not definitively establish, a possible role for cadmium as an etiological agent in human prostate cancer. Further research, however, will be required to establish the precise role of cadmium in this important human malignancy.

The cadmium toxicity hypothesis of aging: a possible explanation for the zinc deficiency hypothesis of aging

Although cadmium and zinc have similar chemical properties, they affect living organisms diversely: while zinc is an essential element for growth, development and functioning of all living cells, cadmium is a highly toxic material. Cadmium has an extremely long biological half-life and may be considered a cumulative toxin. It has been shown to have sterilizing, teratogenic and carcinogenic effects and most of these effects could be reduced or even prevented by zinc administration. An increase in cadmium concentration with age has been proven in various species and in different tissues and these facts led some investigators to the assumption that cadmium accumulation might play an important role in senescence. Zinc essentiality and the lack of a reliable index of intracellular zinc status, formed the rationale for the zinc deficiency hypothesis of aging. This hypothesis suggests a gradual time related zinc deficiency occurring in each living cell, making zinc less available for its metalloenzymes. The sum of all deleterious effects resulting from the distorted function of different zinc enzymes, is later manifested as aging processes. When cadmium concentration increases, zinc concentration in various tissues decreases. Cadmium may inhibit zinc activities at many stages, interfering with zinc absorption, distribution to different tissues and transport into cells or into several intracellular structures. Therefore, it is reasonable to assume that a slowly developing cadmium toxicity may result in a gradual time related zinc deficiency.

Absence of changes in metallothionein RNA in the rat testes made refractory to cadmium toxicity by zinc pretreatment

Testicular toxicity and interstitial cell tumours induced by cadmium are prevented by zinc or by low dose cadmium pretreatments. The mechanism of this tolerance is unknown, though metallothionein (MT) is thought to play a role in tissue resistance to cadmium toxicity. Thus, the possible involvement of the testicular MT gene in metal-induced tolerance to cadmium toxicity was studied. Rats were pretreated with zinc (1.0 mmol kg-1, s.c.). Histological examination of the testes indicated such pretreatments prevented the necrotizing effects of subsequent doses of cadmium (20 mumol kg-1, s.c.) administered 24 h later. RNA was extracted from testes or liver 24 h after zinc pretreatment, and analysed by the slot blot technique using the p2A10 cDNA probe to the MT gene. Zinc pretreatment had little effect on MT RNA in the testes, and such pretreatments did not alter testicular cadmium-binding protein capacity. In contrast, RNAs derived from livers of zinc pretreated rats showed marked increases in MT RNA and MT protein. Hence, the testicular MT gene does not appear to play a major role in the induced tolerance to cadmium toxicity and carcinogenesis generated by zinc.

Toxicological principles of metal carcinogenesis with special emphasis on cadmium

Metals are an important and emerging class of carcinogens. At least three metals, specifically nickel, chromium, and arsenic, are confirmed human carcinogens, and several more are suspected to have carcinogenic potential in man. Considering that the list of known human carcinogens of any type is very small, it becomes clear that metals make up a substantial portion of the list. Furthermore, many metals are very potent carcinogens in laboratory animals. Despite this, relatively little attention has been given to the topic of metal carcinogenesis. The reasons for this relative lack of attention are not clear but perhaps are fostered by a perception that, because metals are the simplest of molecules, their mechanism of action must also be simple. This could not be farther from the truth and, although no clear mechanisms have emerged in the area of metal carcinogenesis, it has become apparent that they are anything but simple. Metal carcinogens possess several unique characteristics including a remarkable target site specificity. Detection of the mechanism, or mechanisms, of metal carcinogenesis has, however, proven elusive, in part because of a wide diversity of metallic carcinogenic agents and the intricate nature of metal interactions in biologic systems. The following review explores this broad topic, with special emphasis on toxicological principles including dose-response relationships and potential mechanisms, using cadmium as an example.

Effect of chronic dietary zinc deficiency on cadmium toxicity and carcinogenesis in the male Wistar [Hsd: (WI)BR] rat

Though it is known that excess zinc will prevent cadmium carcinogenesis, the impact of zinc deficiency on cadmium carcinogenesis has not been defined. This study assessed the effect of dietary zinc deficiency on the carcinogenic potential of cadmium in rats. Groups (n = 28 each) of male Wistar [Hsd: (WI)BR] rats were fed diets adequate (60 ppm) or deficient (7 ppm) in zinc and received a single sc dose of cadmium (5, 10, or 30 mumol Cd/kg). Lesions were assessed over the next 92 weeks. All cadmium doses increased the incidence of testicular interstitial cell tumors. The incidence of cadmium-induced testicular tumors was unaffected by dietary zinc status. However, when multiplicity of testicular lesions was considered, zinc-deficient diets markedly increased the number of testicular interstitial cell adenomas generated by cadmium exposure while significantly reducing the number of preneoplastic lesions (interstitial cell hyperplasias). The combined total number of neoplastic and preneoplastic lesions of the testes was independent of zinc status clearly indicating a shift from hyperplasia to neoplasia within the testes of zinc-deficient rats. The highest cadmium dose (30 mumol/kg) increased injection site sarcomas in zinc-deficient rats (7 tumors/27 rats at risk) but not zinc-adequate rats (3/26) when compared to control (0/49). Chronic progressive renal nephropathy was accelerated by cadmium in zinc-deficient rats. Results indicate that dietary zinc deficiency enhances carcinogenic response at the injection site of cadmium, promotes the neoplastic progression of cadmium-induced testicular lesions, and enhances chronic progressive nephropathy. Thus, dietary zinc deficiency appears to cause a generalized increase in the chronic toxic effects of cadmium.

Morphologic and immunohistochemical characterization of Leydig cell tumor variants in Wistar rats

During a routine long-term drug safety study, lasting approximately 2 1/2 yr, male Wistar rats, treated with a prolactin-inhibiting compound, developed an excess of Leydig cell tumors (LCTs). Most tumors were typical for the rat but a small number showed an unusual variation and some appeared malignant. The variation consisted of glandular and/or tubular structures within the tumor mass which occasionally anastomosed and contained an eosinophilic periodic-acid Schiff (PAS) positive material. In a few of these variants, malignant features such as cellular atypia, capsular, and lymphatic invasion and necrosis were seen. No metastases were detected. Detailed morphological and immunohistochemical investigations were conducted in order to establish the cell of origin of these variants. Glandular/tubular structures were found to stain with varying intensity for vimentin and cytokeratin, but were always negative for beta-tubulin. The results indicated that the cell of origin of these LCT variants was indeed the Leydig cell and that glandular and/or tubular structures within LCTs represented a form of Leydig cell metaplasia.

Studies on the relationship between acute testicular damage and urinary and plasma creatine concentration

A single dose of cadmium chloride (3.23 mumol Cd2+/kg) causing acute testicular damage in male rats also caused significant creatinuria and creatinaemia at 48 h after dosing. Doses of cadmium which did not cause testicular necrosis did not cause creatinuria or creatinaemia. Surgical ligation of the pampiniform plexus also caused ischaemic necrosis of the testis and this was followed by significant creatinuria and creatinaemia. However, neither orchidectomy followed by a toxic dose of cadmium, orchidectomy alone nor sham operation caused significant creatinuria or creatinaemia. Cadmium dosing induced a temporary loss of body weight which was less than that caused by food restriction. Food restriction did not cause significant creatinuria but did cause significant creatinaemia. These data suggest that the creatine is derived from the damaged testis and that measurement of urinary creatine may be a useful non-invasive means of detecting acute testicular damage caused by exposure to chemicals or mechanical impairment of blood flow.

Effects of zinc on the distribution and toxicity of cadmium in isolated interstitial cells of the rat testis

To investigate mechanisms by which zinc prevents cadmium carcinogenicity in the rat testis, the effect of in vivo zinc pretreatment on the distribution, influx, efflux and in vitro cytotoxicity of cadmium in isolated testicular interstitial cells was studied. Zinc pretreatment resulted in marked reduction of cadmium-induced cytotoxicity, as reflected by reduced loss of both intracellular K and glutamic-oxaloacetic transaminase (GOT) from interstitial cells. The subcellular distribution of cadmium was also altered in zinc pretreated cells, with a major shift of cadmium away from the nuclei to other subcellular components such as mitochondria, microsomes and cytosol. In vitro cadmium accumulation in isolated nuclei was also decreased by in vivo zinc pretreatment. In vivo zinc pretreatment also greatly enhanced both influx and efflux of cadmium. These results suggest that a major preventive effect of zinc against cadmium-induced testicular tumors may be due to its ability to reduce the cytotoxicity of cadmium in interstitial cells by enhancing efflux of cadmium and decreasing accumulation of cadmium in nuclei of this target cell population.

Oncogenicity of rat prostate cells transformed in vitro with cadmium chloride

Three rat ventral prostate (RVP) cell lines transformed after in vitro treatment with cadmium chloride (CdCl2) and one control untreated cell line were tested for tumorigenicity in newborn rats. All three cadmium-transformed RVP cell lines induced tumors at the site of inoculation in 95-100% of animals. The fibroblastoid RVP56Cd cell line induced sarcomas, whereas the epithelial cell lines RVP47-3G and RVP47-3F produced highly differentiated squamous cell carcinomas. About 20% of animals injected with RVP47-3G developed lung and splenic metastases. The tumors could be further passaged into young rats. The sarcomas had a hyperdiploid modal chromosome number similar to that of the RVP56Cd cell line. Carcinomas induced by the RVP47-3G cell line had a large proportion of stromal metaphases. The modal chromosome number of these carcinomas was in the hypertriploid-hypotetraploid range, similar to that of the parental cell line. These results demonstrate that treatment of RVP cells with CdCl2 in vitro results in neoplastic transformation. Since both fibroblastoid and epithelial prostate cells have undergone transformation, it seems possible that cadmium acted as a carcinogen without cell specificity. The susceptibility of these cells to the carcinogenic effect may be related to their resistance to cadmium. In the process of neoplastic transformation induced by CdCl2 in RVP epithelial cells changes of squamous metaplasia occur, and probably precede acquisition of tumorigenicity.

Chronic effects on single and multiple oral and subcutaneous cadmium administrations on the testes of Wistar rats

Thirty mature male Wistar rats were administered cadmium as CdCl2 X 1H2O in single doses of 50 mg/kg p.o. or 2.5 mg/kg i.p. or 10 weekly doses of 5 mg/kg p.o. or 0.25 mg/kg i.p., respectively. Ten males, each treated correspondingly with the vehicle, served as control groups. Some of the animals were necropsied after 12 and 18 months, respectively, the remainder were kept for up to 30 months. In a supplementary study 25 males were each treated once with 200 mg/kg p.o. or 2 mg/kg s.c. and 35 males with 100 mg/kg p.o. This experiment was terminated after 6 months. Animals having received 1 X 100 or 1 X 200 mg/kg p.o. or 1 X 2.0 or 1 X 2.5 mg/kg s.c. showed severe lesions of the whole testicular parenchyma with massive calcification of the necrotic tubuli and pronounced fibrosis of the interstitium. All animals receiving 2.5 mg/kg s.c. had a Leydig cell tumor in at least one of the testes. In 5 out of 15 animals surviving 18 months these tumors were classified as malignant (mean time of induction: 858 +/- 77 days). All the other tumors detected were not regarded as causally related to treatment. The results of the supplementary study indicate that with very high oral cadmium dosages Leydig cell tumors may be induceable. Since the massive lesion of the testes appears to be the prerequisite for the occurrence of induced Leydig cell tumors, a non-genetic mechanism is to be assumed in respect to the formation of these tumors.

Carcinogenic effects of cadmium on the prostate of the rat

The carcinogenic effects of cadmium were tested in an animal experiment to check the results of epidemiological studies showing that the incidence of prostatic carcinoma is above average in workers industrially exposed to high cadmium levels. For this purpose 1.9 mg CdCl2 (1.2 mg Cd/kg body weight) was injected into the right ventral prostatic lobe of 12-month-old male inbred rats of the Okamoto-toki strain. Simple hyperplasia was found in 38, atypical hyperplasia in 29, atypical hyperplasia with severe dysplasia in 11 and invasive prostatic carcinoma in 5 of 100 animals 270 days after the injection. Various mechanisms are discussed in connection with the carcinogenic action of cadmium.

Lung aryl hydrocarbon hydroxylase: inhibition following cadmium chloride inhalation

Polycyclic hydrocarbon metabolism in male Sprague-Dawley rats following inhalation of aerosolized cadmium chloride (CdCl2) was examined. Constitutive activity of microsomal aryl hydrocarbon hydroxylase (AHH) (benzo(a)pyrene substrate) was monitored in lung and liver homogenates up to 10 days after exposure. Lung AHH activity was reduced by 85% during the first 2 days following cadmium inhalation, and did not return to normal levels until 7 days after exposure. Enzyme activity in the livers of cadmium-treated animals was similarly depressed (by 65%) within 24 hr. Cadmium inhalation also inhibited (by 50%) 3-methylcholanthrene (MC) induction of lung AHH when compared with MC-treated controls. No significant effect on AHH inducibility by MC was noted in liver homogenates from cadmium-exposed animals. Nonspecific microsomal damage appeared not to occur since glucose-6-phosphatase activity in lung was unaffected by cadmium treatment. Although the mechanism of cadmium's action remains unclear, it appears not to involve a direct interaction of the metal with enzyme. The alteration of AHH activity by cadmium may result from injury to a specific cell type within the lung, which may be a major site of pulmonary AHH activity, or may result from modulation of synthesis and/or degradation of heme proteins in the lung. These results suggest that cadmium, under these conditions, markedly reduces the constitutive and inducible activity of AHH in the lung.

Role of cadmium in carcinogenesis with special reference to cancer of the prostate

It has been shown in animal experiments that injections of large amounts of cadmium cause sarcoma at injection sites or testicular damage and eventually testicular tumors. Long-term exposure with small doses of cadmium has not caused testicular or prostatic tumors in experimental animals. Epidemiological studies on cadmium-exposed workers have shown excess deaths due to prostatic cancer in at least three independent investigations. All reported cases probably had considerable exposure decades ago, but there are not enough data to permit any dose-response calculations. The general epidemiology of prostatic cancer was not taken into account in any of the studies. A review of recent literature on epidemiology of prostatic cancer has revealed some basic facts. Small latent prostatic cancer has been shown to be as common in areas with low mortality from prostatic cancer as in areas with high mortality. In the U.S. the black population has a much higher death rate from prostatic cancer than the white population. Marital status has also been implied as a factor in the development of prostatic cancer. Black populations in Africa have much lower death rates than blacks in the U.S., which may depend on large differences in dietary habits. Thus racial, sexual and nutritional factors might be important for the development of prostatic cancer, since they may influence hormonal status. Cadmium concentrations in testes and prostate increase during heavy exposure, and it has been shown that testosterone synthesis will decrease in cadmium-exposed animals. Excessive exposure may interfere with the zinc/hormone relationship in the prostate, which could be a possible explanation for the development of prostatic cancer in heavily exposed individuals. Direct action of cadmium on the cells is not likely, nor is it probable that low level exposure to cadmium can be a causative factor for prostatic cancer.

Autonomous cortisol secretion by a metastatic Leydig cell carcinoma associated with Klinefelter's syndrome

We present the case of a 39-year-old man with Klinefelter's syndrome and a metastatic Leydig cell carcinoma in whom autonomous cortisol production induced by the interstitial cell tumor was found. Apart from the Cushing's syndrome the endocrine activity of the tumor was demonstrated by the secretion of estradiol, estrone, alkaline phosphatase, and testosterone. This is, to our knowledge, the first description of a Cushing's syndrome not caused via ACTH production but directly induced by ectopic steroid production. While being resistent to chemotherapy and radiation, the tumor responded favorably to treatment with o,p'-DDD. The reduction of tumor size was accompanied by a continuous decrease of serum markers. The etiology of the tumor is discussed in the light of the hormonal derangement caused by the genetic abnormality of Klinefelter's syndrome.

Effects of subtoxic levels of lead and cadmium on urogenital organs of male rats

Higher incidence of prostate cancer among lead and cadmium smelter workers has been reported. Forty male rats were divided into four groups. Group I served as control; Group II was injected intraperitoneally, close to the site of the prostate, with 0.05 mg lead acetate; Group III was injected with 0.05 mg cadmium chloride; and Group IV was injected with a combination of 0.025 mg lead and 0.025 mg cadmium chloride. After daily injection for one month, lead and cadmium had a synergistic effect on testicular damage and prostatic cytology; although no tumor formation was observed in the prostate, there was replacement of columnar epithelium by squamous epithelium, suggestive of progressive, precancerous changes. There was an increase in incidence of stone formation in the kidney and urinary bladder.

A 2 year oral carcinogenicity study with cadmium on rats

A longterm 2-year feeding study on cadmium using CdCl2 . 1H2O has been performed on Wistar-rats. The tested Cd2+-dietary levels were 1, 3, 10 and 50 ppm, respectively. Fifty male and 50 female rats were used for each of the levels. Hundred rats of each sex served as controls. No effects occurred on food intake and survival rate at any dietary level. Growth was unchanged up to 10 ppm whereas 50 ppm resulted in lower weight gain in males only. Histopathological evaluation of a large variety of tissues revealed a number of tumours. Cadmium administered orally was not associated with an increased incidence of total numbers of tumours or of any specific type of neoplasia, although the highest level tested resulted in adverse effects.

A review of the health effects of cadmium

A review of the health effects of cadmium is presented. Overexposure to cadmium produces numerous acute and chronic effects. Cases of acute poisoning resemble metal-fume poisoning. The first and most distinctive indication of chronic effects is renal tubular dysfunction characterized by proteinuria. Other chronic effects include liver damage, emphysema, osteomalacia, neurological impairment, testicular, pancreatic, and adrenal damage, and anemia. Tumorigenic effects have been observed in animals, and excessive prostatic and lung cancer has been observed in worker studies. In vitro and in vivo mutagenic effects have been noted. Cadmium has been shown to cause hypertension in animals; however, it is unclear whether it is capable of causing similar effects in exposed human populations. Normal urinary excretion is less than 2 micrograms/day and correlates with exposure. Normal blood concentration is below 10 ng/gm of whole blood, and although levels are elevated in exposed groups, there is no apparent direct correlation. Hair values correlate well with exposure. Occupational and environmental standards are discussed.

Effects of low doses of ochratoxin A after intratesticular injection in the rat

The toxic effect of various doses of ochratoxin A on the rat testis was investigated after a single intratesticular injection. At time of sacrifice (day 10) degenerating changes occur in the testicular tissues: seminiferous tubules dilatation, cytolysis of the seminiferous epithelium, hyperplasia of the interstitial tissue, vascular thrombosis. The relations between the blood supply disturbances and the observed lesions are discussed.

Mortality and cancer morbidity among cadmium-exposed workers

Preliminary data are reported from a study of 269 cadmium-nickel battery factory workers and 94 cadmium-copper alloy factory workers. The target group comprises all workers with more than 5 years exposure to cadmium at any time since the factories started production. An internal reference group of 328 alloy factory workers without cadmium exposure was also studied. The expected number of deaths and cancers was calculated with the "life-table" method by using national average incidence rates for men in different age groups and at different calendar years. It was found that among the workers in the battery factory who started work before 1948 there was an increased general mortality in the 1950's mainly due to respiratory disease. The same group had an increased renal disease mortality. There was no increase in general cancer mortality or in general cancer incidence. The risk ratio for nasopharyngeal cancer incidence was 10 (two cases), which was statistically significant. For some other sites like prostate, lung and colon-rectum the risk ratios were also greater than 1 but not statistically significant. In the alloy factory there was a tendency for an increased mortality in prostatic cancer (four cases). After correction for the "healthy worker effect" using the reference group, the risk ratio for prostatic cancer deaths was calculated as 2.4, but this was not statistically significant. The findings in this study support the earlier reports of an association between human cadmium exposure and increased risk for prostatic cancer.

Trace element concentrations in renal cell carcinoma

Cadmium, zinc, copper levels and zinc-copper, zinc-bromine, iorn-zinc, iron-copper and iron-bromine ratios are measured in neoplastic and normal kidney samples from humans by the particle induced X-ray emission analysis (PIXE) technique. It is found that cadmium which is normally present in the tubular cells of kidney is not detectable in tumor samples. It is also observed that the zinc-copper ratios in all neoplastic kidney tissues are decreased, but this observation cannot be extended to other element ratios.

Inhibition of mouse testicular DNA synthesis by mutagens and carcinogens as a potential sample mammalian assay for mutagenesis

Since mutagenic substances induce structural changes in DNA, studies were undertaken to determine whether substances would modify DNA replicative activity. DNA synthesis was quantitated 3.5 h after drug administration as uptake into DNA of a 30-min pulse of 10 muCi of [3H] thymidine. Combinations of methylurea (20000 mg/kg) and sodium nitrite (150 mg/kg) administered p.o. resulted in gastric synthesis of nitrosomethylurea and inhibited testicular DNA synthesis by 83%. Combinations of methylurea and sodium nitrite of 1000 and 100 mg/kg respectively inhibited DNA synthesis by 75%. With dimethylamine and sodium nitrite, a combination which results in gastric synthesis of dimethylnitrosamine, inhibitions of 65 and 57% were observed at 2000 mg/kg together with 150 mg/kg and 1000 mg/kg in combination with 100 mg/kg, respectively. In separate experiments, dimethylnitrosamine (50 mg/kg, p.o.) and diethylnitrosamine (100 mg/kg, i.p.) inhibited thymidine uptake by 30 and 89%, respectively. The mutagenic polynucelar hydrocarbon 3-methylcholanthrene (15 mg/kg) inhibited DNA synthesis by 95% and safrole (640 mg/kg), a mutagenic methylenedioxybenzene derivative, inhibited by 60%. Cadmium chloride (10 mg/kg), acetylaminofluorene (160 mg/kg) and dibutylnitrosamine (500 mg/kg) also induced statistically significant effects. Noncarcinogenic analogues of these substances (anthracene, 125 mg/kg; diphenyl-nitrosamine, 500 mg/kg; piperonyl butoxide, 640 mg/kg, and methylurea, 2000 mg/kg in combination with sodium nitrate) were inactive. Highly toxic substances (potassium cyanide, 2.5 mg/kg; 2,4-dinitrophenol, 20 mg/kg; and lead acetate, 150 mg/kg) were also inactive. This index of mutagenicity appears to have considerable sensitivity and therefore may have potential in drug evaluation.

Mutagenicity tests with cadmium in the mouse

The testicle is known to be the critical organ in acute exposure of experimental mammals to cadmium. Such treatment results in temporary sterility and, very often, in the appearance of testicular interstitial cell tumors. The present experiments were performed to determine whether such deleterious effects on the male reproductive organs involved any genetic hazards for the surviving germ cells. The administration of 1.75 mg/kg cadmium chloride to male mice did not increase the dominant lethals during the first three weeks after treatment and failed to induce translocation in the F1 male off-spring. No chromosome rearrangement was observed in the treated males after i.p. injection of 0.5, 1.75 or 3.0 mg/kg cadmium chloride.

Regenerative changes and spermatic granulomas in the rat testis after treatment with DL-ethionine

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The induction of sarcoma in the rat by cadmium sulphide and by cadmium oxide

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