Role of inflammation in chemical-induced hepatotoxicity.

The liver, which is the major organ responsible for the metabolism of drugs and toxic chemicals, is also the primary target organ for many toxic chemicals. Increasing evidence has indicated that inflammatory processes are intimately involved in chemical-induced hepatotoxic processes, and like other inflammatory diseases, such as autoimmunity, are responsible for producing mediators that can effect liver damage or repair. This review will summarize our current understanding of how inflammatory processes influence hepatic pathology and repair following exposure to established hepatotoxic chemicals including carbon tetrachloride, an industrial chemical, and acetaminophen, a widely used analgesic.

The role of tumor necrosis factor alpha in chemical-induced hepatotoxicity.

Only recently have toxicologists come to understand the role of inflammation, and TNFalpha specifically, in classical toxicological processes. This relationship appears fairly complex, as inflammation and proliferation may well be only one facet of a time- and dose-dependent continuum of toxicological and repair processes. Not surprisingly, considerable efforts are being undertaken using our newly found understanding of molecular control to develop specific and safe chemical, biological, and molecular regulators of TNFalpha for potential therapeutic use. Their effectiveness in controlling environmental or occupational diseases has yet to be established.

Comparative pulmonary absorption, distribution, and toxicity of copper gallium diselenide, copper indium diselenide, and cadmium telluride in Sprague-Dawley rats.

Copper gallium diselenide (CGS), copper indium diselenide (CIS), and cadmium telluride (CdTe) are novel compounds used in the photovoltaic and semiconductor industries. This study was conducted to characterize the relative toxicities of these compounds and to evaluate the pulmonary absorption and distribution after intratracheal instillation. Female Sprague-Dawley rats were administered a single equimolar dose (70 mM) of CGS (21 mg/kg), CIS (24 mg/kg), CdTe (17 mg/kg), or saline by intratracheal instillation. Bronchoalveolar lavage fluid (BALF) protein, fibronectin, inflammatory cells, lung hydroxyproline, and tissue distribution were measured 1, 3, 7, 14, and 28 days after instillation. Relative lung weights were significantly increased in CIS- and CdTe-treated rats at most time points. Inflammatory lesions in the lungs consisting of an influx of macrophages, lymphocytes, and PMNs were most severe in CdTe-treated rats, intermediate in CIS-treated rats, and minimal in rats receiving CGS. Hyperplasia of alveolar type 2 cells was present in CIS- and CdTe-treated rats and was greatest in CdTe-treated rats. Pulmonary interstitial fibrosis was observed in CdTe-treated rats at all time points. All three compounds caused marked increases in total BALF cell numbers, with the greatest increase observed in CIS-treated rats. BALF protein, fibronectin, and lung hydroxyproline were significantly increased in all treated animals and were highest in CdTe-treated animals. There was no apparent pulmonary absorption or tissue distribution of CGS. Indium levels increased in extrapulmonary tissues of CIS-treated rats, although Cu and Se levels remained unchanged. CdTe was absorbed from the lung to a greater extent than CGS and CIS. Cd and Te levels decreased in the lung and increased in extrapulmonary tissues. Of these compounds CdTe presents the greatest potential health risk because it causes severe pulmonary inflammation and fibrosis and because it is readily absorbed from the lung may potentially cause extrapulmonary toxicity.

Acetaminophen-induced hepatotoxicity is associated with early changes in AP-1 DNA binding activity.

The AP-1 transcription factor family, which is involved in early response genes, consists of two groups of proteins, Fos-related antigens (fra) and Jun proteins. AP-1 is usually expressed at low basal cellular levels, but can be up-regulated by a variety of exogenous stimuli which results in synthesis of Fos and Jun proteins and increased AP-1 DNA binding activity. Changes in early immediate gene responses are associated with liver necrosis, inflammation and repair, although investigations into their role in drug-induced hepatotoxicity have not been actively examined. In the present studies, we determined that exposure to necrogenic doses of acetaminophen (APAP) was associated with increased AP-1 DNA binding activity in mouse liver. The APAP-induced hepatic AP-1 DNA binding complex had affinity for both the consensus AP-1 and CRE sequences. Furthermore, c-jun, but not c-fos, mRNA transcripts were transiently increased following exposure to hepatotoxic doses of APAP. When endotoxin was administered to mice in order to elicit a hepatic inflammatory response without necrosis, increases in c-jun expression occurred without accompanying changes in AP-1 activity, indicating a different mechanism of action. When compared to conventional indicators of hepatotoxicity, such as plasma levels of liver-associated enzymes, changes in gene expression occurred much earlier and, at least with AP-1 activity, remained activated following normalization of liver enzyme levels. These studies suggest that the AP-1 transcription factor and associated genes are associated in the hepatotoxic response of liver to APAP and may serve as useful molecular biomarkers for chemical-induced hepatotoxicity.

Histopathology of acetaminophen-induced liver changes: role of interleukin 1 alpha and tumor necrosis factor alpha.

Administration of 500 mg/kg acetaminophen (APAP) to female B6C3F1 mice resulted in well-documented pathophysiological changes in the liver manifested as increased serum concentration of liver enzymes (aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and serum sorbitol dehydrogenase), centrilobular congestion, and hepatocellular degeneration and necrosis. The role of proinflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha) and interleukin 1 alpha (IL-1 alpha), on the hepatotoxicity of APAP was examined at 4, 8, 12, and 24 hr following APAP administration. Neutralization of TNF-alpha or IL-1 alpha with specific antibodies partially prevented the hepatotoxic effects of APAP at the 4- and 8-hr time points. In addition, prior administration of anti-TNF-alpha antibodies shortened the recovery time following APAP treatment. While IL-1 receptor antagonist (IL-1ra) had only a modest protective effect against APAP-induced liver damage, as determined by serum enzyme release, IL-1ra had no effect on the degree of hepatic congestion or necrosis at any of the time points examined. On the other hand, administration of antibodies against IL-1ra exacerbated APAP-induced liver toxicity. These results suggest that TNF-alpha and IL-1 alpha play an important role in the degree of damage and recovery that the liver undergoes following APAP intoxication.

Role of proinflammatory cytokines in acetaminophen hepatotoxicity.

Acetaminophen (APAP) intoxication has been shown to activate Kupffer cells. Kupffer cell activation is also associated with the release of proinflammatory cytokines which can induce a variety of pathophysiological responses. These studies examined whether proinflammatory cytokines are produced in response to a hepatotoxic dose of APAP, and if so, the role they play in the observed pathological response. Female B6C3F1 mice received 500 mg APAP/kg in the presence and absence of antibodies against tumor necrosis factor-alpha (TNF-alpha), interleukin-1-alpha (IL-1 alpha), and IL-1 receptor antagonist (IL-1ra). Serum TNF-alpha, IL-1 alpha, and liver-associated enzyme levels were measured. In addition, the levels of mRNA transcripts for IL-1 alpha, IL-6, and TNF-alpha from livers of treated mice were examined by reverse transcription-polymerase chain reaction (RT-PCR). Administration of APAP resulted in an immediate reduction in body temperature as well as elevated serum levels of IL-1 alpha and TNF-alpha that reached a peak at 12 and 16 hr, respectively. The reduction in body temperature was partially blocked by injection of antibodies against TNF-alpha or IL-1 alpha. Furthermore, neutralization of TNF-alpha delayed the increase in serum IL-1 alpha and liver enzyme levels. In contrast, pretreatment with IL-1ra antisera exacerbated the effect of APAP on body temperature and increased the release of liver enzymes. These data suggest that TNF-alpha and IL-1 alpha are released in response to APAP intoxication and are responsible for certain pathological manifestations of APAP-induced hepatotoxicity.

Metal transport in cells: cadmium uptake by rat hepatocytes and renal cortical epithelial cells.

The toxic metals appear to use the transport pathways that exist for biologically essential metals. In this regard interactions between the toxic and essential metals are possible. This report summarizes recent findings on the transport of cadmium in rat hepatocytes and renal cortical epithelial cells in the presence or absence of certain essential metals. The transport of cadmium in hepatocytes does not require energy and, therefore, is not an active process. It occurs primarily (80%) by temperature-sensitive processes, i.e., ion channels and carriers, that involve interaction with sulfhydryl groups. These processes apparently exist for the transport of essential metals like copper, zinc and calcium. The remaining 20% of the cadmium in hepatocytes is transported via a temperature-insensitive process, possibly by diffusion. In comparison with the hepatocytes, a smaller fraction (30%) of the cadmium transport through the basolateral membrane and none from the apical membrane of the renal cortical epithelial cells is temperature-sensitive. Total accumulation through the basolateral membrane is about twice that through the apical membrane. A majority of the cadmium transport in the renal cells is by diffusion. As in hepatocytes, copper, zinc and mercury antagonize cadmium transport through the apical membranes of the renal cells. The relative antagonism by copper is the same (25%); however, the antagonism by zinc (16%) and mercury (10%) is 4- to 6-fold lower than in hepatocytes. It appears that the relative contribution of various transport pathways available for cadmium uptake is different in each cell type and apparently depends on the morphological and functional differences between the cell membranes.

Acetaminophen-induced hepatotoxicity is associated with early changes in NF-kB and NF-IL6 DNA binding activity.

Nuclear transcription factors, such as NF-kB and NF-IL6, are believed to play an important role in regulating the expression of genes that encode for products involved in tissue damage and inflammation and, thus, may represent early biomarkers for chemical toxicities. In the present study changes in DNA binding activity of these factors were examined in livers of mice administered hepatotoxic doses of acetaminophen (APAP). NF-kB and NF-IL6 DNA binding occurred constitutively in control mouse liver. However, within 4 hr following administration of hepatotoxic doses of APAP, their binding activities were transiently lost and is in contrast to AP-1 transcription factor where activation occurs under similar conditions. These changes corresponded with increased release of inflammatory mediators (IL-6, serum amyloid A) and increased levels of enzymatic markers of hepatocyte damage. Similarly, treatment of mice with gadolinium chloride, an inhibitor of Kupffer cell activation and known to protect against APAP-induced hepatotoxicity, reduced the observed pathophysiological response in the liver while altering the APAP-associated changes in NF-kB DNA binding activity. NF-kB was found predominantly in parenchymal and endothelial cells and was composed primarily of relatively inactive p50 homodimer subunits in control liver. Taken together, these studies suggest that hepatotoxicity is associated with early and complex changes in DNA binding activities of specific transcription factors. In particular, NF-kB and NF-IL6 may serve as negative regulators of hepatocyte-derived inflammatory mediators and is analogous to that previously observed in certain other cell systems such as B lymphocytes.

Tumor necrosis factor-alpha and nitric oxide production in endotoxin-primed rats administered carbon tetrachloride.

Tumor necrosis factor-alpha (TNF alpha) is elevated in the sera of rats administered non-lethal doses of carbon tetrachloride (CCl4) followed by endotoxin. Elevated TNF alpha levels are correlated with the increased release of hepatic enzymes indicating hepatic damage. Under these conditions, nitric oxide (NO) was also produced in the liver as evidenced by the formation of nitrosyl complexes which were measured by electron paramagnetic resonance (EPR) spectroscopy. Decreased nitrosyl complex formation occurred in livers following treatment with either an inhibitor or macrophage activation (gadolinium trichloride; GdCl3), an inhibitor of cytokine responses (dexamethasone) or a NO synthase inhibitor (NG-monomethyl-L-arginine; 1-NMA), GdCl3 or dexamethasone treatment decreased, while 1-NMA treatment increased, TNF alpha serum level. Taken together, these data suggest that TNF alpha and NO are induced following CCl4 and LPS exposure and may be important regulators in the hepatotoxicity of this liver injury model.

A protective role for T lymphocytes in asbestos-induced pulmonary inflammation and collagen deposition.

Several lines of evidence have suggested that specific (i.e., lymphocyte) immunity plays a role in chemical-induced pulmonary diseases, including asbestosis. To evaluate the influence of cell-mediated immunity in pulmonary inflammation and fibrosis evoked by asbestos fibers, we compared the effects of asbestos in immunodeficient mice (Balb/c nu/nu and severe combined immunodeficient [C3H-SCID]), immunologically normal mice of the same genetic background, and immunodeficient mice reconstituted with syngeneic T lymphocytes. Increases in lavaged cell numbers occurred in asbestos-treated immunodeficient mice compared with asbestos-treated immunocompetent or immunodeficient mice that received T lymphocytes. Differential analysis of the collected cells in treated mice demonstrated a predominantly neutrophilic infiltrate that correlated with increased levels of leukotriene B4 and prostaglandin E2. There were no significant differences between immunocompetent and athymic asbestos-treated mice in bronchoalveolar lavaged total protein. However, asbestos-treated SCID mice revealed a significant increase in protein content and lactate dehydrogenase activity compared with asbestos-treated normal mice, which did not occur in T lymphocyte-reconstituted SCID mice. Fibronectin levels were elevated in asbestos-exposed athymic mice when compared with air-exposed athymic mice or asbestos-exposed immunocompetent mice. Both asbestos-treated athymic and SCID mice showed a significant increase in total lung hydroxyproline when compared with asbestos-treated immunocompetent mice. Lung hydroxyproline was also reduced in asbestos-exposed SCID mice after T lymphocyte reconstitution and, conversely, increased in T cell-depleted Balb/c mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Asbestos stimulates IL-8 production from human lung epithelial cells.

Studies have indicated that soluble products, including chemotactic factors, released by activated lung macrophages and fibroblasts are critical mediators in the pathogenesis of asbestos-induced pulmonary fibrosis. We provide evidence that mediators produced by lung epithelial cells in response to asbestos may also contribute to lung disease. In the present study, the carcinogenic and fibrogenic fibers, chrysotile and crocidolite asbestos, were shown to directly stimulate the human pulmonary type-II epithelial cell line, A549, and to a lesser degree primary human bronchial epithelial cells, to elicit the chemotactic cytokine IL-8 in the absence of endogenous stimuli such as IL-1 and TNF. That the membrane signaling events responsible for asbestos-induced IL-8 production are distinct from those responsible for IL-8 induction by cytokines was confirmed by using membrane-stabilizing agents and protein synthesis inhibitors. Stimulation was not observed with nonfibrogenic fibers, wollastonite and titanium dioxide, and was the direct result of asbestos-induced initiation of transcription. Asbestos failed to stimulate the release of TNF, IL-1 beta, or monocyte chemoattractant protein-1 in A549 or primary bronchial epithelial cells, indicating that cytokine secretion by asbestos is highly selective. However, a slight release of IL-1 alpha, probably preformed, was released in human bronchial epithelial cells. These data suggest that epithelial cells may, in addition to macrophages and fibroblasts, be an important effector cell in the immunopathogenesis of asbestos-associated diseases and in particular, in the neutrophilic infiltration that is commonly observed after asbestos exposure.

Pulmonary response of Fischer 344 rats to acute nose-only inhalation of indium trichloride.

We have previously shown that rats dosed intratracheally with indium trichloride (InCl3) develop severe lung damage and fibrosis. However, it is not clear what pulmonary effects would result following accidental occupational exposure to low concentrations of indium by inhalation. The present study uses a model of acute lung injury based on single 1-hr nose-only exposures to 0.2, 2.0, or 20 mg InCl3/m3. Exposure to 0.2 mg InCl3/m3 was capable of initiating an inflammatory response. Seven days following inhalation of 20 mg InCl3/m3 the total cell number, fibronectin, and TNF alpha levels in the bronchial alveolar lavage fluid were 8, 40, and 5 times higher than the control, respectively. Commensurate with the level of lung injury 7 days after exposure, an acute restrictive lung lesion and increased airway responsiveness to acetylcholine were observed. Forty-two days after exposure a compensatory increase in lung volume and carbon monoxide diffusing capacity in the 20 mg InCl3/m3 group suggested recovery from the lung injury. Lung collagen levels were increased in a concentration-dependent manner 42 days postexposure. These data indicate that inhalation of InCl3/m3 causes acute inflammatory changes in the lung.

Effect of lead acetate on nitrite production by murine brain endothelial cell cultures.

One of the mechanisms by which lead may cause a perturbation in the nervous system is the alteration of endothelial cell function. This study investigated the effect of lead acetate on constitutive and cytokine-induced production of nitrite, a marker of nitric oxide, in brain microvascular endothelial cells. Nitric oxide synthase may be a target for lead and changes in its function can result in a cascade of physiological effects seen in vivo. Concentrations of 10, 100, and 1000 nM lead acetate, in the presence or absence of 100 ng lipopolysaccharide/ml, 400 U interferon-gamma/ml and 100 U tumor necrosis factor-alpha/ml, were added to confluent cultures of brain microvascular endothelial cells. Concentrations of lead acetate as low as 10 nM decreased constitutive levels of nitrite by 50% without inhibiting the inducible levels. Addition of 1 microM lead acetate had no effect on [3H]L-leucine incorporation, lactate dehydrogenase release, or cellular morphology, indicating that the effect was selective. Increasing the concentration of extracellular calcium to 2 mM abolished the inhibitory effect of lead acetate on the constitutive production of nitrite. These studies suggest that low concentrations of lead are capable of inhibiting nitrite produced by the calcium-dependent constitutive form of nitric oxide synthase while the calcium-independent, inducible form of nitric oxide synthase is not affected. These data provide another testable hypothesis for the as yet undetermined mechanisms of lead neurotoxicity.

Pulmonary toxicity to intratracheally administered indium trichloride in Fischer 344 rats.

The use of indium by the semiconductor industry has risen sharply in recent years with the discovery that the electrical properties of compounds such as indium phosphide and indium arsenide are better than those of silicon. However, relatively little is known about its potential to induce lung damage. These studies examined the effect of indium trichloride (InCl3) on the lung. To examine the disposition and removal of InCl3 from the lung, groups of female Fischer 344 rats received a single intratracheal dose of 1.3 mg In/kg as InCl3 and were euthanized after 1, 2, 4, 7, 14, 28, and 56 days at which time lung samples were analyzed for metal content. Furthermore, the histology, hydroxyproline levels, and bronchoalveolar lavage (BAL) fluid cellularity of the lung were studied. In addition, the effect of 0.00016, 0.00325, 0.065, and 1.3 mg In/kg on inflammatory response and BAL fluid cellularity was compared. While a dose as low as 0.00325 mg In/kg was capable of initiating an influx of inflammatory cells, instillation of 1.3 mg In/kg resulted in an inflammatory response that was still evident 56 days later. After 28 days, the lung weight of the InCl3-treated animals was 2.5 times greater than that of the controls. The total cell number in the BAL fluid of the treated animals after 28 days was 32 times higher than that in the control rats. Sixty-seven percent of these cells were granulocytes. Compared to the controls, the hydroxyproline content of the lungs from the InCl3-treated animals were two-fold greater after 28 and 56 days. Furthermore, the levels of fibronectin and TNF alpha present in the BAL fluid of InCl3-treated rats increased sharply during the first 24 hr and remained elevated 56 days later. These data and the histological examination of the lung following InCl3 treatment suggest that InCl3 is capable of causing severe lung damage and the development of fibrosis.

Comparison of cadmium, mercury and calcium accumulations by isolated hepatocytes of the small skate (Raja erinacea) and rat.

1. Accumulation of calcium, cadmium and mercury by isolated hepatocytes of the small skate (Raja erinacea) and rat was examined at 14 and 37 degrees C, respectively. 2. Metal uptakes by both species were biphasic, with rat cells accumulating more metal than the skate cells. 3. Total accumulation after 30 min was in the order: mercury = cadmium much greater than calcium. 4. In both species calcium and cadmium accumulations were reduced at 4 degrees C, while mercury accumulation was not. 5. Cd accumulation was increased by Cu and Hg in both species. 6. Hg accumulation was inhibited by Cu in both species, and increased by Cd only in the rat cells.

Cadmium and mercury accumulation in rat hepatocytes: interactions with other metal ions.

The uptake of essential metals, such as calcium, copper (Cu), iron (Fe), and zinc (Zn), occurs through processes that include energy-independent carrier mechanisms as well as ion channels. Since cadmium (Cd) and mercury (Hg) inhibit the uptake of these metals, this study examined whether the essential metals in turn affect Cd and Hg accumulation. The uptake of 3 microM Cd was inhibited by Cu, Fe, Zn, and Hg, with 100 microM Zn having the greatest effect. Kinetic analysis indicated that these metals inhibited Cd accumulation in a competitive manner. In comparison, neither the essential metals nor Cd had any significant effect on Hg accumulation. At 4 degrees C the accumulation of Cd was reduced to 20% of that at 37 degrees C, while Hg uptake remained unaffected. The efflux of Cd from the hepatocytes was biphasic, energy-independent, and not affected by Zn, Cu, or Fe. Thus the essential metals decreased Cd accumulation by inhibiting its uptake. On the other hand, Hg decreased Cd accumulation by both inhibiting its uptake and enhancing its efflux. As determined by the organic SH blockers, nearly two-thirds of the Cd entered the hepatocytes through processes involving the SH ligands. The uptake of Hg, however, was not affected by the SH blockers. Furthermore, the fraction of membrane-bound Hg at 3 microM concentration was 2.5 times greater than Cd, indicating that Hg is associated with additional binding sites not utilized by Cd. These results suggest that in hepatocytes Cd uptake occurs mainly through the SH-containing transport processes associated with the uptake of Zn and, to a smaller extent, Cu and Fe. Hg can inhibit Cd uptake by binding to these sites; however, its own uptake occurs via other processes that remain to be elucidated.

Differences in cadmium and mercury uptakes by hepatocytes: role of calcium channels.

Calcium uptake in cells occurs through specific membrane channels. Since cadmium and mercury inhibit calcium uptake, this study examined whether the calcium channels may also be involved in the uptake of these metals. Primary cultures of rat hepatocytes were incubated with 3 microM CdCl2 or HgCl2 in the absence or presence of four different organic calcium channel blockers or a calcium agonist. The calcium channel blockers had no significant effect on mercury accumulation. In comparison, the uptake of cadmium was inhibited by diltiazem and verapmil (50-250 microM) as well as by nifedipine and nitrendipine (25-100 microM), with a maximum inhibition of 31% after 30 min incubation with 250 microM verapamil. The calcium agonist vasopressin (20 nM) increased cadmium accumulation by 15%. This effect was blocked by 250 microM verapamil. Kinetic analysis showed that verapamil decreased the Vmax of cadmium uptake, without altering the Km, indicating a noncompetitive inhibition. The calcium channel blockers were ineffective at 4 degrees C. These data suggest that about a third of the cadmium enters hepatocytes through the calcium channels. The mechanism of mercury uptake, on the other hand, is very different as it does not appear to involve the calcium channels.

Sex differences in hepatic and renal cadmium accumulation and metallothionein induction. Role of estradiol.

The role of estradiol in sex differences in hepatic and renal cadmium accumulation and metallothionein (MT) induction was investigated. Male and female rats and castrated males pretreated with estradiol were injected either i.v. or s.c. with 10 mumol CdCl2/kg. Sex differences in cadmium accumulation and MT induction were apparent after s.c. but not i.v. administration. The female rats accumulated a significantly greater concentration of cadmium in their liver than did the males, as early as 1 hr after the s.c. injection. The elevated levels of cadmium in the females were maintained for at least 10 days. Pretreatment of castrated males with estradiol caused a similarly greater accumulation of cadmium in the liver. Hepatic MT levels peaked in the females at 24 hr and in males 48-72 hr after the cadmium injection and then declined to lower levels. This superinduction of MT occurred only after the s.c. administration of cadmium. MT levels in both sexes plateaued 5 days after the s.c. injection to the levels that were similar to those seen in male and female rats 24 hr after an i.v. injection. In animals injected s.c. with cadmium the renal cadmium levels continued to rise for 5-10 days; however, in animals injected i.v. the levels stabilized within 2 hr. The renal MT levels in the females were significantly higher than in the males. Estradiol pretreatment induced renal MT but did not affect renal cadmium accumulation. Thus, the sex differences in hepatic cadmium accumulation and MT induction are affected by the route and time after the administration of cadmium. Furthermore, estradiol causes a more rapid uptake of cadmium by the liver and also an enhanced induction of MT in both the liver and kidney.

Developmental and sex differences in cadmium distribution and metallothionein induction and localization.

Age- and sex-related differences in hepatic and renal distribution of cadmium (Cd) and the effect of Cd injection (10 mumol/kg) on tissue zinc (Zn), copper (Cu) and metallothionein (MT) levels were investigated in 2- to 84-day old rats. Renal Cd accumulation increased with age of the animal. Sex differences in renal Cd accumulation were noted in young animals where the 2- and 8-day old males had significantly greater concentration than the females. There were no clear effects of Cd on renal Zn. Renal Cu levels, however, were elevated in the adults. The adult females contained about twice as much MT as the adult males. Cd treatment had no effect on renal MT levels of 8- to 84-day old animals but depressed the levels in 2-day old. Age-related increase in hepatic Cd accumulation was also found; the pattern was more clear cut in females than in males. In addition, in the females the hepatic Cd concentration was significantly higher than in the males. Cd-injection significantly increased hepatic Zn and MT concentrations only in weaned animals. While there were no sex differences in MT levels in the young animals, the weaned females had significantly more MT than the corresponding males. Immunohistochemical staining for MT showed positive staining in both cytoplasm and nuclei of the parenchymal cells. The number of MT-positive nuclei was dependent on the relative MT concentration of the liver. In spite of the intense nuclear staining in 2-day old controls and 84-day old Cd-injected rats, less than 1% of the hepatic MT was present in the nuclear fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypersensitivity of cultured ataxia-telangiectasia cells to etoposide.

Fibroblasts from patients with ataxia-telangiectasia (A-T) were found to be hypersensitive to killing by the antineoplastic agent etoposide. The A-T fibroblast strains GM5823, GM367, and GM2052 were twofold to threefold more sensitive to killing by etoposide than fibroblasts from normal controls (AG1521, AG1522, and IMR90). A simian virus 40 (SV40)-transformed, immortal human fibroblast line (GM5849) derived from the A-T cell line GM5823 was also studied. GM5849 retained the unusual sensitivity of nontransformed A-T fibroblast lines to x-irradiation, bleomycin, and neocarzinostatin (zinostatin). GM5849 was also more sensitive to etoposide than were SV40-transformed fibroblasts from normal controls. M1, and SV40-transformed fibroblast line derived from a patient with xeroderma pigmentosum, had the same sensitivity to etoposide as SV40-transformed fibroblasts derived from normal controls.