A perspective on In vitro developmental neurotoxicity test assay results: An expert panel review.

For decades, there has been increasing concern about the potential developmental neurotoxicity (DNT) associated with chemicals. Regulatory agencies have historically utilized standardized in vivo testing to evaluate DNT. Owing to considerations including higher-throughput screening for DNT, reduction in animal use, and potential cost efficiencies, the development of alternative new approach methods (NAMs) occurred; specifically, the advent of the DNT in vitro test battery (DNT IVB). SciPinion convened an expert panel to address specific questions related to the interpretation of in vitro DNT test data. The consensus of the expert panel was that the DNT IVB might be used during initial screening, but it is not presently a complete or surrogate approach to determine whether a chemical is a DNT in humans. By itself, the DNT IVB does not have the ability to capture nuances and complexity of the developing nervous system and associated outcomes including behavioral ontogeny, motor activity, sensory function, and learning/memory. Presently, such developmental landmarks cannot be adequately assessed in the DNT IVB or by other NAMs. The expert panel (all who serve as co-authors of this review) recommended that additional data generation and validation is required before the DNT IVB can be considered for application within global regulatory frameworks for decision-making.

Persistence of cadmium-induced metabolic changes in liver and kidney.

Daily intraperitoneal injection of cadmium chloride (1 milligram per kilogram) for 45 days enhanced gluconeogenesis as evidenced by significant increases in the activities of liver and kidney cortex pyruvate carboxylase, phosphopyruvate carboxylase, hexosediphosphatase, and glucose-6-phosphatase, the quartet of key, rate-limiting enzymes involved in the biotransformation of noncarbohydrate precursors into glucose. Whereas cadmium treatment decreased the level of hepatic glycogen, the concentration of blood glucose and urea was significantly elevated by this heavy metal. Discontinuation of the heavy metal treatment for 28 days, in rats previously injected with cadmium for 45 days, failed to restore the observed biochemical alterations in hepatic and renal carbohydrate metabolism to control values. Evidence indicates that cadmium augments the glucose-synthesizing capacity of liver and kidney cortex and that various metabolic changes persist even after a 4-week period of withdrawal from exposure to the heavy metal.

Neurobehavioral alterations in rats exposed to acrylonitrile in drinking water.

This study was carried out on rodents, to explore the neurobehavioral effects of acrylonitrile (AN) administered in drinking water. Thirty, male, Sprague-Dawley rats were randomly divided into three groups: two exposure groups (50 and 200 ppm AN), and one control group (tap water without AN). Three tests, including the open field test, rotarod test and spatial water maze, were applied to evaluate locomotor activities, motor co-ordination and learning and memory, respectively, prior to initiation of the treatment, and at Week 4, 8 and 12 postexposure. There were no consistent changes in the open field test, except for locomotion and grooming episodes. In the rotarod test, AN significantly decreased the latencies to fall in a dose and time-dependent manner. In the spatial water maze test, rats exposed to AN for 12 weeks had significantly more training times and longer escape latencies than control animals. These findings indicate that oral exposure to AN induces neurobehavioral alterations in rats.

Renal and hepatic concentrations of platinum: relationship to cisplatin time, dose, and nephrotoxicity.

Autopsy tissues were obtained from 30 patients who had received cisplatin antemortem; the tissues were assayed for platinum by flameless atomic absorption spectrometry. Patients with antemortem evidence of renal toxicity had higher renal cortical platinum concentrations than did patients without evidence of kidney damage. In addition, patients with nephrotoxicity were more likely than patients without toxicity to have renal cortical platinum concentrations that were higher than renal medullary platinum concentrations. Overall, the two variables most closely associated with an increase in serum creatinine with treatment were renal cortical platinum concentration (P less than .02) and cumulative dose of cisplatin (P less than .05). These two variables were important independently of one another. Renal cortex platinum concentrations correlated inversely with time from last treatment until death, whereas hepatic platinum concentrations did not. In contrast, hepatic platinum concentrations correlated with dose of cisplatin while renal platinum concentrations did not. Our results suggest the following: (1) cisplatin-induced renal toxicity is tissue-platinum-concentration dependent and cisplatin-dose dependent; and (2) cisplatin may be handled differently at the molecular level in liver and kidney.

Chlorphentermine-induced alterations in pulmonary phospholipid content in rats.

Daily, intraperitoneal administration of the anorectic drug chlorphentermine (30 mg/kg) for 5 days to rats significantly increased phosphatidylcholine and total phospholipid content after 1 week and reached a maximal level 4 weeks after treatment in whole lung tissue (unlavaged lungs) and in sessile tissue in which alveolar lipids and macrophages were removed by pulmonary lavage (lavaged lungs). In lavaged lung, a significant rise in the content of sphingomyelin, phosphatidylserine plus phosphatidylinositol component, and phosphatidylethanolamine plus phosphatidylglycerol fraction occurred after 2 weeks, remained at this increased level for 4 weeks, and was followed by a return to control amounts after 5 weeks. In unlavaged lung, the chlorphentermine-induced elevation in sphingomyelin content seen after 1 week persisted at this same significant level even 5 weeks after treatment. Regardless of experimental duration, pulmonary glycogen levels were not altered markedly by chlorphentermine in unlavaged or lavaged tissue. Phenobarbital (30 mg/kg) did not markedly alter pulmonary glycogen and phospholipid component levels. Simultaneous phenobarbital and anorectic drug administration prevented the chlorphentermine-induced rise in total phospholipid, sphingomyelin, and phosphatidylcholine in unlavaged lung without a change in glycogen. A 7-day withdrawal from chlorphentermine treatment in rats previously injected with drug for 2 weeks resulted in a return to control in the levels of sphingomyelin, phosphatidylcholine, and total phospholipid in unlavaged lung. Extension of withdrawal from treatment for 2 weeks produced a significant decrease in all phospholipid components below control values, suggesting that a possible imbalance in synthetic and catabolic activity may persist after drug removal. The concentration of lung glycogen was not altered significantly by chlorphentermine treatment or withdrawal from drug administration. Our results indicate that the chlorphentermine-induced rise in phospholipid components was time-dependent in lavaged and unlavaged lungs, and the increase in phosphatidylcholine occurred independently of a change in glycogen. In addition, the present study shows that the chlorphentermine-induced changes in phospholipid levels are reversible and almost completely prevented by phenobarbital.

Adverse effects of drugs and chemicals in breast milk on the nursing infant.

Breastfeeding is an essential physiologic process that provides nutrition to the infant and protects the child against infection and immunologic disorders. The incidence of various diseases and metabolic disorders is known to be less in a breastfed infant compared with a child given a milk substitute. Psychologically, a breastfed infant forms a maternal bond that enables adaptation more readily to a social environment. It is well-established that all drugs are excreted into breast milk and are bioavailable to the infant. In general the majority of drugs do not pose a significant problem to the nursing infant and breastfeeding should be encouraged. The physician should be aware of which drugs are contraindicated during lactation and which drugs should be used with caution. There are also environmental chemicals that readily enter breast milk and may induce adverse effects. At present, the advantages of breastfeeding for infant development outweigh the potential adverse consequences and this physiologic process should be encouraged. With the use of available data on pharmacokinetics, milk-to-plasma ratio, excretion, etc. a supportive approach can be delineated by the pediatrician to reassure the nursing mother that they can safely breastfeed and continue therapy with minimal effects on the infant. It is thus imperative to document the extent to which a drug or chemical appears in breast milk and any apparent effects in the infant.

Drug-induced phospholipidosis: are there functional consequences?

Phospholipidosis induced by drugs with a cationic amphiphilic structure is a generalized condition in humans and animals that is characterized by an intracellular accumulation of phospholipids and the concurrent development of concentric lamellar bodies. The primary mechanism responsible for the development of phospholipidosis is an inhibition of lysosomal phospholipase activity by the drugs. While the biochemical and ultrastructural features of the condition have been well characterized, much less effort has been directed toward understanding whether the condition has adverse effects on the organism. While there are a few cationic amphiphilic drugs that have been reported to cause phospholipidosis in humans, the principal concern with this condition is in the pharmaceutical industry during preclinical testing. While this class of drugs should technically be referred to as cationic lipophilic, the term cationic amphiphilic is widely used and recognized in this field, and for this reason, the terminology cationic amphiphilic drugs (CADs) will be employed in this Minireview. The aim of this Minireview is to provide an evaluation of the state of knowledge on the functional consequences of CAD-induced phospholipidosis.

Confounding factors in toxicity testing.

The necessity for understanding normal human functions and the mechanisms which underlie dysfunction in these processes is essential in the promotion of a healthier lifestyle. To achieve this goal utilization of a suitable animal model is necessary in order to develop new pharmaceutical agents to alleviate diseases or chemicals to enhance the quality of life. It is incumbent upon investigators to choose a species in which pharmacokinetic principles are established and it is important that these phenomena resemble those of the humans. The choice of rats has specific advantages in that these rodents possess similar pharmacodynamic parameters to humans. Other advantages include availability, low cost, ease of breeding, and an extensive literature data-base to enable comparisons to present findings. However, in the interpretation of data from animals to humans, there are factors which need to be recognized as playing important roles in chemical-induced outcomes. The confounding factors include strain, supplier, age, gender, hormonal status and dietary intake. The aim of this article is to demonstrate that there are differences in the responsiveness of rat stock/strains to chemicals and that lack of consideration of confounding factors yields inappropriate conclusions regarding risk assessment for humans.

Systematically applied chemicals that damage lung tissue.

A large, and increasing number of drugs and chemicals have been found which are toxic to lung following systemic administration. These agents damage lung tissue specifically, or in addition to damage to other tissues. Mechanisms explaining the pulmonary damage produced by some lung toxins have been uncovered. These include concentration of the agent within lung, the absence of adequate pulmonary detoxication systems, and bioactivation to a toxic species within specific lung cells or at distant sites followed by transport to the lung. The basic biochemical lesions underlying lung damage, responses of individual lung cells and pulmonary repair processes to the toxic agent, and species and age differences in susceptibility to lung damage have not, however, been well defined for most lung toxins. This review describes the information available on pulmonary biochemical and pathological changes associated with some of these lung-toxic agents. In addition, mechanisms proposed to explain the lung damage are discussed. The agents covered include: paraquat, the thioureas, butylated hydroxytoluene, the trialkylphosphorothioates, various lung-toxic furans and antineoplastic agents, the pyrrolizidine alkaloids, metals and organometallic compounds, amphiphilic agents, hydrocarbons, oleic acid, 3-methylindole, and diabetogenic agents. Detailed reviews on the overall toxicity of many of these agents have been published elsewhere. This review concentrates on their pulmonary toxicity. Information is presented as an overview to illustrate both the extensive literature that is available and the important questions that remain to be answered about systemic chemicals that damage lung tissue.

Renal and hepatic nucleic acid metabolism in neonates: relation to experimental duration, chlorphentermine dose as well as subsequent withdrawal.

Daily oral administration of either 20, 40 or 60 mg/kg chlorphentermine for 7 days significantly increased liver and kidney DNA levels, which were not elevated further even after a 3 week treatment period. Although cessation of drug administration for 3 weeks resulted in a return of hepatic DNA levels to control values, a rise in renal DNA was still observed after this withdrawal period. Whereas 20 mg/kg chlorphentermine for 7 days failed to markedly alter the incorporation of thymidine into kidney and liver DNA, significant enhancement was noted in neonates receiving 40 or 60 mg/kg drug and quantitatively greater incorporation occurred when the agent was given for 21 days. While a signficant augmentation in nucleic acids synthesis was seen 1 week after animals were removed from 40 or 60 mg/kg anorectic, a restoration to control levels occurred after a 3 week abstinence period. Treatment with 20 mg/kg for 1 week followed by withdrawal resulted in a significant rise in the incorporation of thymidine into renal and hepatic DNA. In contrast, drug administration for 3 weeks followed by 21 days abstinence resulted in a return to control levels in the incorporation of thymidine into kidney and liver DNA, except for renal tissue removed from 20 mg/kg. Our data demonstrate that the chlorphentermine-induced alterations in renal and hepatic DNA metabolism are dose-dependent, related to duration of exposure as well as reversible.

Effects of subsacute and chronic lead treatment on glucose homeostasis and renal cyclic AMP metabolism in rats.

The effects of chronic oral ingestion of lead in doses ranging from 20-80 ppm were compared with those seen after the subacute exposure of rats to a 10 mg/kg daily dose of the heavy metal for 7 days. Irrespective of the treatment regimen used, lead treatment significantly increased the activities of renal pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-diphosphatase and glucose 6-phosphatase. The observed enhancement of kidney gluconeogenic enzymes in chronically treated animals was associated with a stimulation of the adenylate cyclase-cyclic AMP system, a rise in blood blucose and urea as well as a depression in hepatic glycogen and serum immunoreactive insulin (IRI) levels. In contrast, subacute exposure to lead failed to significantly alter cyclic AMP metabolism and the concentrations of liver glycogen, blood glucose, serum urea or IRI. Whwereas the insulinogenic index (the ratio of serum IRI to blood glucose concentration) was markedly suppressed in chronically treated rats, this ratio remained within normal limits following subacute exposure to the heavy metal. However, a marked decrease in the insulinogenic index was observed in subacutely treated rats 15 min after the administration of a glucose load. The data provide evidence to show that increased glucose synthesis as well as suppressed pancreatic function may be responsible for lead-induced disturbances in glucose homeostasis.

Comparative evaluation of amiodarone-induced phospholipidosis and drug accumulation in Fischer-344 and Sprague-Dawley rats.

Amiodarone (AD) and its major metabolite, desethylamiodarone (desethylAD), are both phospholipogenic. The present study was undertaken to evaluate the comparative susceptibilities of male Fischer-344 and Sprague-Dawley rats to AD-induced phospholipidosis in alveolar macrophages (AMs), liver and kidney tissue and the concomitant accumulation of AD and desethylAD in these cells, tissues and plasma. Rats were administered AD (100 mg/kg/day, p.o.) for 1 week. Plasma concentrations of AD and desethylAD were approximately 4- and 12-fold higher, respectively, in Fischer-344s compared to Sprague-Dawleys 24 h after the last dose. AD and desethylAD levels in AMs were approximately 12- and 25-fold higher, respectively, in Fischer-344s than Sprague-Dawleys. In the liver and kidney, levels of both compounds were also significantly higher in Fischer-344s than Sprague-Dawleys. Ultrastructural features indicative of phospholipidosis were not observed consistently in any tissue except AMs from treated Fischer-344s. AM total phospholipid increased nearly 5-fold in Fischer-344s, while Sprague-Dawleys showed no increase over control. AMs from both strains incubated with 10 microM AD or desethylAD in vitro were not significantly different in their accumulation of the compounds. When incubated with AD or desethylAD, the lysosomal phospholipases A1 partially purified from AMs of both strains were equally sensitive to inhibition as measured by the drug concentration giving 50% inhibition in activity (IC50). The results of this study indicate that at the same administered dose, AD and desethylAD, accumulate to higher tissue levels and are more phospholipogenic in male Fischer-344 rats than in male Sprague-Dawley rats. The basis for the high susceptibility of Fischer-344 rats to AM-induced phospholipidosis is unknown at present but appears not to be related to biochemical or cellular features of the AMs.

Effect of over-the-counter drugs on the unborn child: what is known and how should this influence prescribing?

The developing organism is unique in its responsiveness to drugs. The predictability of therapeutic effectiveness and safety of drugs in pregnancy using the adult as a model for pharmacokinetics and pharmacodynamics can result in grave consequences in the fetus. There exists a general misconception that since over-the-counter (OTC) drugs are readily available, these pharmaceutical agents can be viewed as safe to use by adults. Ingestion of OTC preparations during pregnancy results in placental transfer and accumulation of these drugs in the fetus. As the fetus lacks the ability to handle pharmaceutical agents, since renal function, metabolic pathways, etc. are not fully developed, drug exposure in utero may produce deleterious effects in the fetus but not the mother. Clinicians are aware of drug-induced effects on the fetus and have dramatically reduced the use of prescription drugs during pregnancy. However, the use of self-medication (OTC) has significantly increased during pregnancy through extensive, effective advertising by the pharmaceutical industry and lack of sufficient data indicating an OTC effect on the fetus. However, the consequences of OTC drug use need to be established, since these compounds continue to be used extensively, especially during pregnancy.

In vivo oxidation of reduced nicotinamide-adenine dinucleotide phosphate by paraquat and diquat in rat lung.

Intravenous injection of rats with 156 mumol/kg of paraquat or 140 mumol/kg of diquat produced, within 60 min, a sharp drop in the ratios of NADPH to NADP in lung. The effect persisted for a time period of at least 24 h. Exposure to 100% oxygen enhanced the toxicity of both compounds without substantially amplifying changes in the NADPH/NADP ratio. Lungs retained the capability to synthesize adenine nucleotides de novo. Electron microscopic studies showed that both paraquat and diquat damage type I alveolar cells, but only paraquat produces type II cell lesions. Although bipyridylium herbicides produce acute oxidation of NADPH in vivo, there seems not to exist a straightforward relationship between this event and cell damage.

Biochemical paramters of BHT-induced cell growth in mouse lung.

Male mice of 7 different strains were injected i.p. with 400 mg/kg of butylated hydroxytoluene (BHT). 2 and 4 days later, the incorporation of thymidine into pulmonary DNA was significantly increased in all treated animals and this was accompanied by an increase in lung weight and pulmonary DNA. Thymidine kinase activity and DNA polymerase activity were enhanced in the lungs of BHT-treated animals and maximum activity of these enzymes appeared to precede maximum thymidine incorporation by 24 h. 3 days after BHT a good correlation was found between administered dose and thymidine kinase activity. Measuring the activity of this enzyme might serve as a convenient biochemical marker to follow and to quantitate BHT-produced cell proliferation in lung. The concentrations of cyclic AMP and the activity of adenylate cyclase were not altered by BHT on days 1-9 after administration. BHT produced also some dose-dependent, time-dependent increases in the activities of pulmonary 5'-nucleotidase and glucose-6-phosphate dehydrogenase (G6PDH), but had little effect on isocitric dehydrogenase (ICDH), pyruvate kinase (PK) and lactic dehydrogenase (LDH).

Pathogenic factors in aminoglycoside-induced nephrotoxicity.

Aminoglycoside antibiotics play an integral role in antimicrobial chemotherapy. Unfortunately, these drugs are known to cause nephrotoxicity in man and experimental animals. In fact, the incidence of renal dysfunction during the course of clinical treatment with aminoglycoside antibiotics is approximately 10%. Over the past two decades the elucidation of the pathogenesis of aminoglycoside-induced nephrotoxicity has been the subject of numerous investigations. This review describes the recent theories postulated to play a role in the pathogenesis of antibiotic-induced renal damage. In particular, the importance of amino-glycoside levels in the renal cortex or at the membrane binding site is examined in detail. The relevance of antibiotic tissue levels is reflected in the ability of other drugs to modify nephrotoxicity through an alteration in renal aminoglycoside content. The role of factors including age and diet in drug-induced nephrotoxicity is described. In clinical practice, aminoglycoside antibiotics may often be with other agents. The influence of aminoglycoside interaction with other drugs including vancomycin, cephalosporins and cytotoxic drugs is examined in the light of reports that nephrotoxicity is potentiated in these situations. In addition, this review focuses on the role of infection (pyelonephritis and septicemia) and bacterial endotoxin as pathogenic factors involved in aminoglycoside nephrotoxicity. Both the direct influence of endotoxin and the indirect effects of vasoactive mediators and inflammatory processes will be discussed. A multiplicity of factors is involved in the pathogenesis of aminoglycoside-induced nephrotoxicity and these are further amplified in the presence of infection.

Effects of parenteral vanadium administration on pulmonary metabolism of rats.

Daily, intraperitoneal administration of either vanadium pentoxide (VP) or sodium vanadate (NaV) at a dose of 1 mg/kg for 14 days produced no marked change in pulmonary protein, glycogen and phospholipid (PL) levels of adult male rats. Increasing the VP dose to 4 mg/kg decreased lung PL content, while an equivalent NaV dose elevated tissue glycogen. Treatment with either dosage of NaV elevated the activities of pulmonary 6-phosphogluconate dehydrogenase (6PGDH), pyruvate kinase (PK) and glutathione peroxidase (GP), and the higher dose increased lactate dehydrogenase (LDH) and glutathione reductase (GR). The 1 mg/kg VP produced a significant rise in glucose-6-phosphate dehydrogenase (G6PDH) and 6PGDH. while the higher VP dose in general failed to alter enzymic activity. Our data suggest that similar to intratracheal instillation, parenteral administration of vanadium exerts an effect on lung metabolism of rats.

Ultrastructural and biochemical alterations in the livers from chick embryos maintained in shell-less culture.

Ultrastructural and biochemical studies were conducted on the livers from chick embryos maintained in shell-less culture up to stage 39 (Hamburger-Hamilton) and from control embryos developed in ovo up to the same stage. The ultrastructural characteristics of hepatic cells from the cultured embryos were similar to those found in the controls except that they contained many large lipid droplets and were almost devoid of lipoprotein granules normally associated with the Golgi complex and the smooth endoplasmic reticulum. These changes suggest the existence of alterations in the lipid metabolism. The livers from cultured embryos showed also a decreased incorporation of tritiated leucine into proteins, which indicates a reduced rate of protein synthesis. These results are consistent with previous reports showing that cultured embryos possess hypoproteinemia. Lactic dehydrogenase activity was similar and pyruvic kinase higher in the livers from cultured with respect to control embryos. This appears to indicate that both aerobic and anaerobic glycolysis were not depressed and that the changes observed in the rate of protein synthesis should not be attributed to hypoxia. "Fat-storing cells" similar to those described in mammals were found both in control and cultured embryos. They had not been previously described in the livers from chick embryos.

Platinum concentrations in human autopsy tumor samples.

Platinum concentrations were determined in autopsy tumor samples obtained from 27 patients who had received cisplatin 40-1,029 mg/m2 from 0 to 240 days antemortem. Liver metastases had significantly higher platinum concentrations than did tumors in other sites (p less than 0.005). Platinum concentrations in liver metastases were similar to platinum concentrations in normal liver. Platinum concentrations in gliomas and brain metastases were similar to platinum concentrations in other extrahepatic tumors. Platinum concentration generally decreased with increasing distance into brain from tumor. By multiple stepwise linear regression analysis, the factors that were independently most closely associated with tumor platinum concentration were time from last cisplatin treatment, cumulative lifetime dose of cisplatin, route of cisplatin administration (intraarterial vs. other), and site of tumor deposit (liver vs. other) (r = 0.69, p less than 0.001). Patients whose tumors had responded to cisplatin-containing regimens had mean tumor platinum concentrations that were higher than the mean tumor platinum concentrations in patients whose tumors had not responded to cisplatin (p less than 0.05).

The use of morphologic tissue examinations as novel technique for estimation of drug adverse reactions in hospitalized patients.

Morphologic evaluation of tissue specimens from a hospital population was used to identify and classify adverse reactions to drugs. With the use of this novel technique, the incidence of adverse tissue reactions was found to be 3.6% out of which 1.5% were found to be definitely caused by a specific pharmacological agent. Adverse tissue reactions were both sex- and age-related occurring more often in women and more frequently between the ages of 51-60 years. Although adverse tissue reactions were noted less frequently in males, a definite causative agent was identified in over 50% of males in which a tissue reaction was observed. Endometrium and liver were the predominant tissues altered morphologically in our hospital population. Estrogenic preparations and alcohol were found to be most frequently implicated in the observed adverse tissue reactions. In comparison to the observation of symptoms associated with drug use, our study provides an alternate means of relating an adverse reaction to pharmacological agent employed in that subjective bias can successfully be removed. Although the present system described appears to be more rigorous in identification of adverse reactions, evidence indicates that tissue adverse reaction technique may be advantageous in determination of an unwanted response in patients under 60 years of age. It is hoped that the tissue adverse reaction evaluation may provide a more accurate prediction of possible adverse effects and perhaps may be a more reliable, sensitive system for estimation of adverse effects in hospitalized patients.