Embryotoxic and teratogenic effects of interaction of cadmium and lindane in rats

Embryotoxic and teratogenic effects of cadmium and lindane were studied in rats. Cadmium or lindane alone did not produce any significant malformations in the 20 day old foetuses whereas their combination caused significant reduction in the body weight of dams and pups and increased total embryonic deaths. Skeletal deformities like wavy ribs, reduced skull ossification and reduced caudal vertebrae were potentiated in coexposure group. The study indicated that the simultaneous exposure to cadmium and lindane may have more deleterious effects on the developing foetus compared to either alone.     

Embryotoxic effect of cadmium on rats upon oral administration

The dose/effect relationships and/or threshold doses for embryotoxicity of cadmium in rats were studied by administering cadmium chloride both in food or by oral gavage. From the 6th to the 15th day of pregnancy, the animals were given either 1.2, 3.5, or 12.5 mg/kg body wt of Cd²⁺ in the food, or 1.8, 6.1, 18.4, or 61.3 mg/kg body wt of Cd²⁺ by oral gavage. The “no toxic-effect” doses for embryotoxic effects were 12.5 (feeding) and 6.1 mg/kg body wt of Cd²⁺ (oral gavage). These values are higher than the amount stated by WHO as safe for man (500 μg/person per week) by approx 8000 and 4000 times, respectively.     

Embryotoxic and teratogenic effects of indium chloride in rats and rabbits

Daily indium chloride doses of control (0), 50, 100, 200, or 400 mg/kg were administered orally to Sprague-Dawley rats by gavage, on d 6-15 of gestation, and daily metal doses of control (0), 50, 100, or 200 mg/kg were administered to New Zealand rabbits on d 6-20 of gestation. Further groups of pregnant rats were treated with control (0) or 400 mg/kg indium chloride orally on one of d 8, 9, 10, 11, 12, 13, 14, or 15 of gestation. The dams and fetuses were examined on d 21 (rats) and 30 (rabbits) of gestation, using standard teratological methods. Indium concentration was determined in the maternal and fetal blood, as well as in the amniotic fluid, by atomic absorption spectrometry. Indium was found to cross the placenta and appeared in fetal blood in proportion to the metal concentration of the maternal blood. In the amniotic fluid, indium concentrations remained below the detection limit. In rats, indium chloride produced dose-dependent maternal toxic effects, with a dose of 400 mg/kg inducing embryotoxicity (embryolethality) and teratogenicity. Doses of 200 and 100 mg/kg were embryotoxic (retarding) and teratogenic, causing skeletal and visceral anomalies in addition to external anomalies (rudimentary or missing tail, syndactylia, clubfoot, exencephalia) in rats. In rabbits, 200 mg/kg indium chloride was lethal for the dams and the embryos (some of the animals died, and the number of abortions and full resorptions increased). This dose was found to be teratogenic (caused gross renal anomalies) and increased the frequency of fetuses with skeletal retardation. In rats, the effects of indium chloride causing fetal retardation was found to be independent of exposure time. The teratogenic effects were the highest on d 11 and 12 of gestation, when indium chloride caused gross external malformations. Data suggest that the teratogenic effects of indium chloride can be attributed primarily to a direct cytotoxic action of indium resulting from placental transfer, but the effect is not a selective one, as it appears only in the presence of maternal toxic effects.     

Embryotoxic effects of Solanum lycocarpum St. Hill fruits consumption during preimplantation and organogenesis in rats

Solanum lycocarpum St. Hill is a common plant in the Brazilian savanna. This plant has an alkaloid with stereospecific configuration to the synthesis of steroid hormones. Since the plant may be consumed by pregnant animals, the present study was undertaken to determine the possible embryotoxic effects of S. lycocarpum fruit ingestion (3% added to the diet) during preimplantation (from the first to the sixth days of gestation) or during organogenesis in rats (from the sixth to the sixteenth days of gestation). Few differences were observed in food and water consumption without biological importance. The placental weight in the group that received the plant during the organogenesis period was decreased. An increase in sternebra abnormalities was observed in animals treated with the plant during organogenesis. Olfactory bulb hemorrhage was increased in the group that received the plant during preimplantation when compared to the control group. These results indicate that consumption of S. lycocarpum at 3% in diet during pregnancy cause slight toxicological effects. Other studies have to be conducted to better investigate the causes of toxicity and other toxic effects of higher levels of exposure to this plant.     

Nervous system effects of dissolved and nanoparticulate cadmium in rats in subacute exposure

Cadmium, a toxic heavy metal with various applications in technology, can affect people both by environmental (foodborne) and occupational (inhalation) exposure and can cause nervous system damage. To model this, rats were subacutely treated either with CdCl(2) solution per os (3.0 mg kg(-1) b.w.) or nanoparticulate CdO(2) (particle size ca 65 nm) by intratracheal instillation (0.04 mg kg(-1) b.w.) alone or in sequential combination. Nervous system effects were observed at different levels of function (open field behavior, cortical electrical activity, nerve action potential) and some general toxicological indicators were also measured. Three weeks of oral plus one week of intratracheal exposure caused significant reduction of body weight gain and open field motility. Lengthening of latency of sensory evoked potentials, observed in all treated rats, was also the most significant in the group receiving oral plus intratracheal treatment. Conduction velocity of the tail nerve was likewise decreased in all treated groups. Several of the effects pointed to a potentiating interaction between the two forms of Cd. Modeling environmental and occupational Cd exposure by oral and intratracheal application in rats was feasible, with results suggesting serious negative health effects in humans suffering such a combined exposure.     

Toxicological effects of cadmium during pregnancy in Wistar albino rats

Cadmium is a heavy metal and widespread environmental toxicant. This study investigated the effects of prenatal Cd exposure on fetal growth and limb development in rats. Pregnant rats were given 0, 4 or 8 mg/kg/day (equivalent to ≈ 0, 30 or 60 ppm) of cadmium as CdSO₄ in their drinking water from conception to gestation day 20. Cd significantly (p<0.001) and dose-dependently inhibited maternal weight gain and caused abortion of pregnancy. In addition, Cd significantly (p<0.001) decreased fetal body weight, forelimb and hindlimb bone lengths, compared to controls. These effects were sex-dependent, greater in the female offspring. Furthermore, there were reductions in the weights, and alterations in the histology of maternal placenta, ovary and liver of Cd-exposed rats. The results indicate that cadmium will cause abortion of pregnancy and sex-dependent impairment of fetal growth and limb development, which may be consequent upon alterations in ovarian and placental functions.     

Effect of long-term inhalation exposure to cadmium oxide fumes on cardiac muscle ultrastructure in rats

The ultrastructure of the cardiac muscle of rats exposed 5 h daily, 5 days a week to cadmium oxide (CdO) fumes at a concentration of 0.16 mg Cd/m3 for 3 and 6 months and at a concentration of 1 mg Cd/m3 for 3 and 4 months has been evaluated. The structure of muscle cells, arterioles and capillaries remained unchanged. There were distinct alterations of the intercalated disc structure dependent upon the level and time of exposure. The damage to intercalated discs varied from the enlargement of the fissure between membranes (within unspecialized segments) to disruption of the complex junctions.     

Biochemical and morphological effects of long-term inhalation exposure of rats to ethylbenzene

Male Wistar rats were exposed (six hours/day, five days/week) to 0, 50, 300 or 600 p.p.m. of ethylbenzene vapour in the air, and killed after 2, 5, 9 or 16 weeks of exposure. After 600 p.p.m., liver-microsomal protein but not cytochrome P-450 concn. was slightly increased; NADPH-cytochrome c reductase was increased maximally by 30% (1.3-fold), 7-ethoxycoumarin O-deethylase (1.8-fold) and UDPG-transferase (2.3-fold). The increase in liver-cytosolic D-glucuronolactone dehydrogenase paralleled the glucuronidation activity (less than or equal to 2-fold). In the kidneys, only 7-ethoxycoumarin O-deethylase (less than or equal to 3.5-fold) and UDPG-transferase (less than or equal to 1.8-fold) showed dose-related increases. Ethylbenzene exposure did not deplete hepatic glutathione (GSH); kidney GSH was slightly increased (less than or equal to 1.3-fold) according to dose. Urine excretion of thioethers was increased with dose, and at 600 p.p.m. was eight times control levels. At 600 p.p.m. there was no increase in serum alanine aminotransferase activity, and liver cells showed slight proliferation of smooth endoplasmic reticulum, slight degranulation and splitting of rough endoplasmic reticulum and enlarged mitochondria, but no necrosis.     

Reversibility effects on renal and hepatic gluconeogenic enzymes in rats from chronic exposure of cadmium

The reversibility of cadmium chloride (CdCl2) effects on renal and hepatic gluconeogenic enzymes in rats was studied by removal of CdCl2 from the diet. Adult, male Sprague-Dawley rats were continuously treated with 0, 25, 50, and 75 ppm CdCl2 mixed in powdered diet for 180 d. After this period of chronic exposure, all treated rats were kept on CdCl2-free diet for another period of 180 d. The CdCl2 induced serum glucose and activities of glucose 6-phosphatase, fructose 1, 6-bisphosphatase, and phosphoenolpyruvate carboxykinase reversed to the levels of control values 120 d after the rats were fed with CdCl2-free diet. There were no significant differences in measured enzyme activities either 120 or 180 d after the cessation of CdCl2 treatment. The data indicate that CdCl2 effects on gluconeogenesis will gradually recover with time when the metal is removed from the diet.     

Renal kallikrein excretion as a distal nephrotoxicity marker during cadmium exposure in rats

Cadmium exposure is known to induce hypertension, but development of hypertension is not universal in exposed animals. However, the cellular uptake of cadmium could also exert renal cytotoxic effects which have been, until now, essentially only studied at the proximal tubule level. Kallikrein is an enzyme synthetized in renal cortex and excreted in the urine in the distal tubule. Therefore, to evaluate the distal renal effect of cadmium, we studied the daily urinary kallikrein excretion (UKE) in conscious unrestrained female Brown Norway rats during long-term chronic exposure to 2 dosages of cadmium given subcutaneously 3 times a week, a low dose (LD): 0.25 mg/kg and a high dose (HD): 1 mg/kg. Neither dose of cadmium was able to induce significant hypertension in the treated animals. HD administration for 24 weeks resulted in a decreased UKE associated with an increase in plasma renin activity and sodium and potassium excretions. LD administration had no significant effect on UKE. Twenty weeks after stopping cadmium administration, a persistent reduction in UKE was still observed; furthermore, the group which had been previously administered a LD of cadmium, now also exhibited a reduced UKE. During this re-examination period in both groups, the UKE reductions were associated with normal systolic blood pressure, glycosuria, natriuresis. Our data show that cadmium administration can influence UKE, plasma renin activity, plasma aldosterone concentration and electrolyte excretion without inducing any variation of blood pressure. This may reflect a nephrotoxic, non-hypertensive effect. Since this effect persisted after stopping cadmium administration, it may indicate a prolonged irreversible nephrotoxic effect at the distal nephron level. Thus, UKE may be a useful non-invasive index to evaluate distal nephrotoxicity.     

Neurotoxic effects of cadmium in young rats

This study examined the effects of cadmium on the brain of male, Sprague-Dawley rats of different ages. Cadmium was more toxic in 4-day-old than in adult rats, thus 2 and 4 mg/kg were given sc to the younger rats and 4 and 6 mg/kg to the older rats. The lower doses resulted in no mortality and the higher dose about 10% mortality in both groups. Four days after a sc injection of cadmium chloride (4 mg Cd/kg) to 4-day-old rats, lesions were evident in the corpus callosum, caudate-putamen, and cerebellum, while 2 mg/kg of cadmium produced only slight cerebellar damage. Nineteen days after injection of 4 mg Cd/kg to 4-day-old rats, a large cystic cavity was evident where the corpus callosum is normally located. In contrast, cadmium did not produce any observable brain damage in adult rats at 4 or 6 mg/kg, either 4 or 19 days after injection. Eighteen days after treatment, hyperactivity was evident in newborn rats exposed to 4 mg/kg of cadmium, but not in newborn rats exposed to 2 mg/kg of cadmium or in adult rats treated with 4 or 6 mg/kg of cadmium. Thus, cadmium at a dose that produces only a few deaths is toxic to the brain of newborn rats, as evident by hyperactivity and lesions.     

Tissue cadmium and locomotor behavior following acute inhalation exposure to cadmium aerosol in rats

Rats were exposed for 1 h to increasing concentrations of cadmium (Cd) through inhalation of cadmium chloride aerosol using nose-only inhalation chambers and depositions of Cd in lungs, liver and kidneys were measured. Changes in spontaneous locomotor activities were recorded 2 and 7 d after cessation of exposure. A concentration dependent increase in Cd in lungs, liver and kidneys was accompanied by significant alterations in spontaneous locomotor response that was dependent on the air Cd concentrations and the postexposure duration. The study shows decreased spontaneous locomotor activity due to Cd accumulation in tissues.     

Embryotoxic effects of L-691,121, a class III antiarrhythmic agent,in rats

 L-691,121 is a class III antiarrhythmic agent which blocks potassium currents, leading to prolongation of cardiac potential and prevention of cardiac arrhythmia. In a developmental toxicity study in rats, there was a dose-dependent decrease in embryonic/fetal survival, and death of the entire litter was seen at an oral dose of 0.8 mg/kg per day. The critical period for embryolethality was determined as gestational days (GD) 10–13. In a study where females received 1 mg/kg on a critical day (GD 10 or 12) and were killed at 24-h intervals, a high embryonic mortality was seen at 72 h (GD 10 treatment) or 48 h (GD 12 treatment) after dosing. The surviving embryos had morphological abnormalities such as enlarged cardiac tube and pericardium, generalized edema, and hematoma. In order to investigate a possible mechanism for the embryolethality, GD 11 embryos were dissected from females at 4 h after dosing of 1 mg/kg and incubated for 5 h in vitro. The embryonic heart rates were decreased for the first 2 h after incubation but tended to recover to control levels thereafter. When GD 11 embryos were incubated for 4 h with the drug, there were decreases in the heart rates during the entire observation period. In a wash-out study where the embryos were transferred to drug-free medium after 1-h exposure, decreased heart rates recovered to control levels. In GD 11 embryos cultured for 24 h with the drug, there were gross abnormalities that consisted of altered yolk sac and embryonic circulation, and enlargement of cardiac tube and pericardium similar to those seen in the preceding in vivo study. These results suggest that decreased heart rates, reduced yolk sac circulation and the associated morphological abnormalities induced by L-691,121 are related to the embryolethality in rats. Received: 14 December 1993 / Accepted: 16 March 1994     

Embryotoxic effects of CKD-602, a new camptothecin anticancer agent, in rats

CKD-602 is a newly developed camptothecin anticancer agent. Preclinical studies suggest that it may have greater antitumor activity and lower toxicity than other camptothecin anticancer agents. The potential of CKD-602 to induce embryotoxicity was investigated in the Sprague-Dawley rat. One hundred mated females (sperm in vaginal lavage=day 0) were distributed among three treatment groups and a control group. CKD-602 was administered intravenously at dose levels of 0, 5, 20 and 80 microg/kg/d to pregnant rats from days 6 to 15 of gestation. The vehicle control rats received an equivalent volume of 1 ml distilled water with d-mannitol 50mg and tartaric acid 0.06 mg. All dams were subjected to the caesarean section on day 20 of gestation. There were no signs of maternal toxicity or embryotoxicity at 5 microg/kg/d, but at 20 microg/kg/d, there was an increase in relative brain weight. At 80 microg/kg/d, reduced food intake, suppressed body weight and increased weight of spleen were observed in dams. An increase in the resorptions and dead fetuses, a decrease in litter size, fetal and placental weights were also found. In addition, various types of external, visceral and skeletal malformations occurred. Characteristic malformations included absent eye bulge, agnathia, dilated cerebral ventricle, anophthalmia, absent thoracic centrum, fused vertebral arch, fused rib, among others. Visceral and skeletal variations were observed. Retarded ossification of several skeletal districts and delayed ossification of sternebrae, metatarsals and sacrocaudal vertebrae were also observed. The results show that CKD-602 is embryotoxic and teratogenic at a minimally maternally toxic dose, i.e. at 80 microg/kg/d in rats. The no-observed-adverse-effect level (NOAEL) of CKD-602 for developmental toxicity was considered to be 20 microg/kg/d, however, the NOAEL for maternal toxicity was 5 microg/kg/d.     

Low-level cadmium exposure increases one-way avoidance in juvenile rats

Twenty-seven pregnant rats from three genetic lines, Roman High Avoidance (RHA), Roman Low Avoidance (RLA), and Satinder's Heterogeneous Stock (SHS), received daily SC injections of either 0.075 mg/kg CdCl₂ (low dose), 0.225 mg/kg CdCl₂ (high dose), or an equivalent volume of saline vehicle (control) throughout gestation. Cd-exposed progeny from the RHA genetic line weighed significantly less than RHA control progeny (pd 35–44); however, SHS progeny from the low-dose group weighed significantly more than progeny from any other group (pd 14–44). Unconditioned escape response (UER) level was determined on pd 39. Progeny from the high-dose group required a significantly lower UER level as compared to the low-dose group. Acquisition of conditioned avoidance responses was tested from pd 41 to 44. There were significant differences due to dose for one-way avoidance responses. Cd-related differences in one-way avoidance were restricted to progeny from the SHS genetic line. SHS progeny from the high-dose group demonstrated significantly more one-way responses when compared to the control group. Differences in avoidance responses are discussed in relation to Cd-induced hyper-nociception. The concentration of Cd in the liver and kidney of dams and progeny was determined by Inductively Coupled Plasma spectroscopy (ICP). There were significant dose-related differences in Cd concentration in maternal tissues.     

Acute cadmium exposure and ovarian steroidogenesis in cycling and pregnant rats

The purpose of this study was to evaluate the effect(s) of acute in vivo cadmium (Cd) exposure on steroidogenesis in rat ovaries during different reproductive states. Sprague-Dawley rats were injected subcutaneously on the day of diestrus, or on day 7 or 16 of gestation with a single dose of 0, 3, or 5 mg Cd/ kg bw, and evaluated 24 h later. Serum progesterone and estradiol concentrations were determined. Whole-ovary culture was used to evaluate Cd effects on the production of progesterone, testosterone, and estradiol. Liver, kidney, spleen, ovary, placenta, and blood were analyzed for Cd and iron (Fe) concentrations. No general toxic effects, no disruption of estrous cyclicity, and no change in fetal viability were seen. Histologic evaluation revealed moderate Cd-related thecal congestion in ovaries of pregnant rats. The highest Cd concentrations, except for liver, were found in the fetal portion of the placenta. Interestingly, Cd-related decreases in Fe concentration were found in several tissues from rats in proestrus and on gestation day 8, and in fetal placenta from rats on gestation day 17. Cadmium appears to interfere with normal steroidogenesis at a number of sites in the biosynthetic pathway with serum estradiol concentration and ovarian estradiol production the most affected. Acute Cd effects on steroidogenesis are most severe in rats evaluated in proestrus or in early pregnancy, while in late pregnancy steroidogenesis is relatively unaffected.     

Ethanol self-administration in rats following exposure to dietary cadmium

Rats were maintained on an ad lib diet containing 100 ppm cadmium (Group Cadmium-Diet) or a control diet with no added cadmium (Group Control-Diet). After 55 days of exposure to their respective diets, animals were tested for fluid intake using a nonchoice procedure that presented a 15% ethanol solution in the home cage for 5 days. Subsequently, all animals were offered a 10% ethanol solution or tap water in a 3-bottle, 2-fluid choice test in the home cage. This fluid intake test was conducted for a 5 day baseline period, and then again concurrently with avoidance acquisition (14 days) and extinction (4 days) training on a free operant (Sidman) avoidance task that required animals to lever press to avoid electric footshock. After training was terminated the choice test was continued further in the home cage for a 15 day post-avoidance period. Ethanol intake was greater for animals exposed to cadmium on all tests of fluid consumption, and all animals consumed more ethanol during the periods following termination of the stressor (avoidance extinction, post-avoidance) than during the actual period of stress (avoidance acquisition). Interpretive comments focus on the effects of cadmium on stress reactivity, sensory processing, and metabolism.