Chloroquine treatment does not cause phospholipid storage by depleting rat liver lysosomes of acid phospholipase A.

Chronic treatment of rats with chloroquine causes phospholipid storage in the lysosomes of liver and other tissues. This could be due to chloroquine-induced depletion of liver lysosomal phospholipase A. Alternatively, it could be caused by chloroquine inhibition of intralysosomal phospholipid catabolism. We treated rats with chloroquine in a dosage schedule sufficient to cause a 35% increase in liver phospholipid content. Acid phospholipase A activity was increased in liver homogenates and in lysosomal preparations obtained from chloroquine-treated animals. Thus, while fibroblasts respond to chloroquine treatment by cellular depletion of certain acid hydrolases as shown by others, the levels of acid phospholipase A increase in liver. Our results provide additional new support for the hypothesis that inhibition of lysosomal phospholipase A activity is the major mechanism of chloroquine-induced phospholipidosis.

Alterations in rat alveolar surfactant phospholipids and proteins induced by administration of chlorphentermine.

Chlorphentermine is a cationic amphiphilic drug which produces a phospholipid storage disorder in rat lungs. Experiments were carried out to characterize changes in the composition of acellular alveolar lavage materials and to study possible mechanisms by which pulmonary surfactant phospholipidosis is produced by administration of the drug. Following ten daily injections of chlorphentermine (25 mg/kg body weight), there are 12.2- and 13.6-fold increases of pulmonary lavage total phospholipids and disaturated phosphatidylcholines (disaturated PC), respectively. In addition, there is a 2.8-fold increase in total protein and a 12.7-fold increase in the surfactant apoprotein group with molecular weights from 28,000 to 32,000. We measured incorporation of labeled palmitate, choline and glycerol into disaturated PC in type II cells and alveolar macrophages isolated from control and chlorphentermine-treated animals. The drug does not affect the incorporation of labeled substrates into disaturated PC in either cell type. However, in alveolar macrophages there is a decrease in the rate of intracellular degradation of recently synthesized disaturated PC in chlorphentermine-treated animals. The drug also inhibits the phospholipase-induced catabolism of rat surfactant disaturated PC which occurs during incubation of alveolar lavage fluid in vitro at 37 degrees C. When the lavage fluid is divided into subfractions by differential centrifugation, a larger percentage of the phospholipid is distributed in the less sedimentable subfractions in chlorphentermine-treated animals relative to controls, suggesting the accumulation of older surfactant materials. These results suggest that chlorphentermine-induced phospholipidosis of pulmonary surfactant materials is due to decreased rates of phospholipid degradation.

Role of phospholipase A inhibition in amiodarone pulmonary toxicity in rats.

Amiodarone is effective in the treatment of ventricular and supraventricular arrhythmias. In man its clinical use is associated with the accumulation of phospholipid-rich multilamellar inclusions in various tissues including lung, liver and others. This report presents evidence showing that amiodarone is a potent inhibitor of lysosomal phospholipase A from rat alveolar macrophages, J-744 macrophages and rat liver. When compared with other cationic amphiphilic agents which are known to produce phospholipidosis, amiodarone is one of the most potent inhibitors yet discovered. The subcellular localization of amiodarone has been determined in lung and its distribution was consistent with a lysosomal localization. It is hypothesized that amiodarone causes cellular phospholipidosis by concentrating in lysosomes and inhibiting phospholipid catabolism.

Association of chlorphentermine with phospholipids in rat alveolar lavage materials, alveolar macrophages and type II cells.

Administration of chlorphentermine to rats leads to an increase in the phospholipid content of pulmonary surfactant materials and alveolar macrophages. It is known that this drug binds to pure phospholipids and prevents their degradation by phospholipases. Therefore, experiments were carried out to determine if chlorphentermine binds to surfactant phospholipids in vitro and to measure the in vivo association of drug with phospholipids in alveolar lavage materials from rats injected with [14C]chlorphentermine. The presence of chlorphentermine in alveolar macrophages, type II cells and other small pneumocytes (a population of lung cells which does not include alveolar macrophages or type II cells) from treated animals was also assessed. Binding of the drug to surfactant phospholipids, as measured with the fluorescent probe, 1-anilino-8-naphthalene sulfonate, occurs in vitro and does not differ in various subfractions of alveolar lavage materials isolated by differential centrifugation. Following daily administration of chlorphentermine to rats for 3 days, the drug appears to be associated with surfactant phospholipids such that the molar ratio is 1:100 (chlorphentermine/phospholipid). Chlorphentermine is also associated with alveolar macrophages (molar ratio, 1:18) and type II cells (molar ratio, 1:33). Not much drug is associated with the population of other lung cells (molar ratio, 1:333). In alveolar macrophages, approx. 70% of the drug seems to be bound to phospholipid and/or sequestered in subcellular organelles. However, only 20% of the chlorphentermine is bound and/or sequestered in type II cells. The results of these experiments suggest that following chlorphentermine administration, the drug is associated with phospholipids in acellular pulmonary lavage materials, alveolar macrophages and type II cells. This drug-phospholipid interaction may impair phospholipid degradation and lead to a phospholipidosis in surfactant materials and alveolar macrophages.

Accumulation of amiodarone and desethylamiodarone by rat alveolar macrophages in cell culture.

Amiodarone is a clinically effective antiarrhythmic drug shown to cause lung damage in humans and animals. While the mechanism of this pulmonary toxicity is unknown, it may be associated with the accumulation of amiodarone and its principal metabolite, desethylamiodarone, by alveolar macrophages. In the present study, characteristics of the uptake of these drugs by rat alveolar macrophages in vitro were examined. The alveolar macrophages were collected by pulmonary lavage from male Fischer 344 rats. Amiodarone and desethylamiodarone were incubated separately (2.5 microM) with the cells in culture for 1, 2, 4 and 18 hr. High performance liquid chromatography was used to measure drug uptake. At 1 and 2 hr, the uptake of desethylamiodarone by alveolar macrophages was significantly greater (P less than 0.05) than that of amiodarone, but over time, the accumulation of amiodarone began to approach that of desethylamiodarone and was not significantly different by 4 hr. To simulate a more physiological situation, plasma levels achieved in the adult male rat after 1 week of amiodarone treatment (150 mg/kg) were used. Amiodarone (1.95 micrograms/mL) and desethylamiodarone (0.80 microgram/mL) were added together into the cell culture. At 1 and 18 hr, the ratio of desethylamiodarone/amiodarone uptake was significantly greater (P less than 0.05) than in incubation medium containing no cells, indicating an enhanced uptake of desethylamiodarone. Metabolic inhibitors (KCN, 2,4-dinitrophenol, and ouabain) and other cationic, amphiphilic drugs (chlorcyclizine, chlorphentermine, and imipramine) were added individually to the cell cultures containing amiodarone or desethylamiodarone. During 1 hr of incubation, these agents had no effect in blocking the accumulation of amiodarone and desethylamiodarone in the cells. The efflux of amiodarone or desethylamiodarone was measured from cells following incubation for 4 hr with each drug. After this time, the medium was replaced with drug-free medium, and the cells were incubated for another 24 hr. Sixty-three percent of amiodarone was lost as compared to only 31% of desethylamiodarone over the 24-hr period (P less than 0.05). The results of this study are suggestive of a preferential uptake and retention of desethylamiodarone as compared to amiodarone. The accumulation of the drugs appears not to be due to active transport or associated with any carrier protein involved in the transport of other structurally-related compounds.

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.

Oxidant-mediated electronic excitation of imipramine.

The interaction of imipramine with both resting and zymosan-activated human polymorphonuclear leukocytes (PMNs) resulted in the generation of chemiluminescence (CL). This CL was not accompanied, however, by an enhanced release of superoxide anion. CL was also observed following the interaction of imipramine with either a xanthine oxidase or a horseradish peroxidase catalyzed system. Collectively, these observations support the concept that the CL elicited from these interactions is reflective of the electronic excitation of the imipramine molecule. In contrast to the response seen with PMNs, addition of imipramine to resting alveolar macrophages (AMs) failed to yield CL. However, CL from imipramine was observed with resting AMs upon supplementation with exogenous horseradish peroxidase. The lack of response with control AMs and the significant inhibition of the imipramine-PMN CL by the myeloperoxidase inhibitor azide suggests that a peroxidase-derived oxidant facilitated the oxidation of imipramine, yielding a product in an electronically excited state. In addition to PMNs, CL was elicited from imipramine by rat or rabbit liver microsomes, suggesting that PMNs may be a useful model system to predict a xenobiotic effect on the CL response elicited by other cellular oxidant-generating systems. Moreover, these observations underscore the possibility that the metabolic activation of drugs by PMNs may be of pharmacologic and toxicologic importance.

Acute silica toxicity: attenuation by amiodarone-induced pulmonary phospholipidosis.

Exposure to the toxic mineral dust silica has been shown to produce an acute inflammatory response in the lungs of both humans and laboratory animals. Coating silica with phospholipids reduces its toxicity when studied with in vitro systems. The drug amiodarone increases phospholipid within the cells, airways, and alveoli of the lungs. This increase in phospholipid is due to amiodarone's ability to inhibit phospholipase activity within alveolar macrophages (AMs) and whole lung. The purpose of this study was to determine whether the amiodarone-induced increase in pulmonary phospholipid would protect the lungs from acute damage caused by the intratracheal instillation of silica. Treatment of male Fischer 344 rats with amiodarone for 14 days caused an increase in phospholipid content in bronchoalveolar lavage fluid and AMs compared to vehicle-treated controls. The rats were then instilled with silica or saline vehicle. At both 1 and 14 days after silica exposure, pulmonary phospholipidosis was associated with a marked reduction in acute silica-induced pulmonary damage as assessed by biochemical parameters in bronchoalveolar lavage fluid, however, the influx of neutrophils into the airspaces was not reduced. Four times more phospholipid was bound to the silica recovered from amiodarone-treated rats compared to controls. The results of these in vivo experiments indicate that pulmonary phospholipidosis attenuates the acute damage associated with the intratracheal instillation of silica in rats. By using an in vitro cell culture system, we demonstrated that, in contrast to control AMs, phospholipidotic AMs were significantly more resistant to the cytotoxicity of surfactant-coated silica.(ABSTRACT TRUNCATED AT 250 WORDS)

Introduction of luminol-dependent chemiluminescence as a method to study silica inflammation in the tissue and phagocytic cells of rat lung.

The inhalation of silica has been shown to produce a dramatic inflammatory and toxic response within the lungs of humans and laboratory animals. A variety of cellular and biochemical parameters are used to assess the silica-induced lung injury. The purpose of this paper is to introduce the use of luminol-dependent chemiluminescence as a new method to study inflammation in both phagocytic cells and lung tissue recovered from silica-exposed animals. Chemiluminescence, or the emission of light, accompanies the release of reactive forms of oxygen when phagocytic cells are challenged. In this study, male Fischer 344 rats were intratracheally instilled with either silica (10 mg/100 g bw) or saline vehicle. One day after the instillations, a marked increase in the chemiluminescence was observed in the lung tissue and bronchoalveolar lavage cells recovered from the silica-treated animals when compared with the saline controls. The light reaction was markedly decreased by either superoxide dismutase of N-nitro-arginine methyl ester hydrochloride. Superoxide dismutase is involved in the enzymatic breakdown of superoxide anion, while N-nitro-L-arginine methyl ester hydrocholoride, a nitric oxide synthase inhibitor, prevents the formation of nitric oxide. When superoxide anion and nitric oxide react, they form the highly oxidizing substance peroxynitrite. This study then implicates peroxynitrite as an agent that may be responsible for some of the oxidant lung injury that is associated with silica exposure. The use of luminol-dependent chemiluminescence may prove valuable as a method to measure the earliest events in the inflammatory process, and may be an adjunct in studying the mechanisms that produce inflammation.

Spinosad insecticide: subchronic and chronic toxicity and lack of carcinogenicity in CD-1 mice.

The potential toxicologic and oncogenic effects of spinosad, a natural fermentation product with insecticidal properties, were investigated. The 13-week toxicity study consisted of groups of 10 CD-1 mice/sex provided diets containing 0, 0.005, 0.015, 0.045, or 0.12% spinosad (Study 1). The 0.12% group was terminated on Test Day 44 due to mortality and overt clinical signs of toxicity. An 18-month chronic oncogenicity study consisted of groups of 50 CD-1 mice/sex provided diets containing 0, 0.0025, 0.008, or 0.036% spinosad (Study 2). Two interim groups of 10 mice/sex/group were terminated after 3 and 12 months. Females given 0.036% were terminated on Day 455 due to markedly lower body weights and feed consumption, as well as excessive mortality. Because of the early termination of the female high-dose group, additional groups of 10 male and female mice (12-month interim necrospy) and 50 male and female mice (18-month necropsy) were provided diets containing 0, 0.0008, or 0.024% spinosad (Study 3) to fully assess potential chronic toxicity and oncogenicity. Standard toxicologic parameters were evaluated consistent with existing regulatory guidelines. The primary effect in the 13-week and 18-month studies was intracellular vacuolation of histiocytic and epithelial cells in numerous tissues and organs at doses of > or = 0.015%. The histological vacuolation corresponded to ultrastructural lysosomal lamellar inclusion bodies. This alteration was consistent with phospholipidosis, a condition that results from accumulation of polar lipids in lysosomes. Lesions with no apparent direct relation to vacuolation were hyperplasia of the glandular mucosa of the stomach, skeletal muscle myopathy, bone marrow necrosis, and anemia with associated splenic hematopoiesis. The incidence of tumors in mice given spinosad was not increased relative to controls at any dose level. The no observed effect level for the 13-week study was 0.005% (6 mg/kg/day) spinosad, and for the chronic toxicity/oncogenicity study was 0.008% (11 mg/kg/day) spinosad for male and female CD-1 mice.

Spinosad insecticide: subchronic and chronic toxicity and lack of carcinogenicity in Fischer 344 rats.

Spinosad is an insecticide derived from a naturally occurring bacterium via fermentation. The toxicity of spinosad was characterized in subchronic and chronic toxicity/oncogenicity studies conducted according to standard toxicology regulatory guidelines. Subchronic toxicity was evaluated in groups of 10 Fischer 344 rats/sex given feed containing 0, 0.05, 0.1, 0.2, or 0.4% spinosad (Study 1) or 0, 0.003, 0.006, 0.012, or 0.06% spinosad (Study 2) for 13 weeks. Lower body weights and increased mortality occurred in rats given 0.4% spinosad. Microscopic effects were observed in the adrenal glands, liver, lymphoid cells, reproductive tissues, kidney, thyroid, stomach, lung, and skeletal muscle of rats given > or = 0.05% spinosad, and consisted primarily of vacuolation of cells; however, degenerative, regenerative, and/or inflammatory changes were also noted in some tissues. Vacuolation within a number of tissues was ultrastructurally characterized by an increase in size and number of lysosomes that contained extensive membranous whorls consistent with phospholipidosis. The no observed effect level (NOEL) in the 13-week studies was 0.012% (24 mg/kg/day) spinosad. Chronic toxicity and oncogenicity were evaluated in groups of 60 Fischer 344 rats/sex given feed containing 0, 0.005, 0.02, 0.05, or 0.1% spinosad for up to 2 years. Rats given 0.1% spinosad for 1 year had microscopic effects similar to those observed in the subchronic studies. Vacuolation and inflammation of the thyroid gland also occurred in rats given 0.05% spinosad for 1 year. Excessive mortality occurred in rats from the oncogenicity study given 0.1% spinosad by 21 months, and surviving rats were euthanized because the maximum tolerated dose had been exceeded. Rats given 0.05% spinosad for 2 years had vacuolation and/or inflammation involving the thyroid, lymphoid tissue, and lung. Rats given 0.05% spinosad had similar numbers of neoplasms as control rats, indicating that spinosad was not carcinogenic at dose levels up to 0.05%. The NOEL at 2 years was 0.005% (2.4 mg/kg/day) spinosad.

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.

Cumene hydroperoxide-mediated lipid peroxidation in rat alveolar macrophages following induction of phospholipidosis with chlorphentermine.

Rats were treated for 4 weeks with chlorphentermine hydrochloride (30 mg/kg, i.p., 5 days/seek), a regimen which causes a profound phospholipidosis in the alveolar macrophages (AMs). The susceptibility of these lipid-laden cells to lipid peroxidation was examined and compared to AMs from control (untreated) rats. Lipid peroxidation was induced in cells in vitro by incubation with cumene hydroperoxide (10(-5) M--10(-3) M). A dose dependent increase in malonyl dialdehyde (MDA) formation was observed with both populations of AMs. Two to three times more MDA was found in lipidotic AMs than controls at the higher dose of cumene hydroperoxide. Under these conditions, less loss of cellular viability resulted with the lipidotic AMs than controls. The partial depletion of reduced glutathione in the cells led to an even greater MDA formation by both cell-types with the lipidotic AMs being more markedly affected. Both populations of AMs experienced a greater loss of viability associated with loss of reduced glutathione with the control AMs showing more toxicity than the lipidotic cells. Therefore, while the induction of phospholipidosis renders AMs more suspectible to lipid peroxidation, they show less of a loss in cellular viability than control cells. The previously reported augmentation in the antioxidant defense mechanisms in the lipidotic cells may be partially responsible for these results.

Drug-induced lipidosis and the alveolar macrophage.

The alveolar macrophage is the principal component of the defense mechanisms of the lung. As a result, alterations in its function can predispose the host organism to pulmonary disease or damage. This cell shows toxic responses to a wide variety of chemicals which are delivered to the lungs by either inhalation or via the systemic circulation. In this regard, this review will focus on the effects of a group of cationic amphiphilic drugs which when administered to humans and animals causes a lysosomal storage disorder of lipids, principally phospholipids, in alveolar macrophages. The susceptibility to the disorder is species-dependent and can be induced in fetal, neonatal and adult animals. Evidence exists that the accumulation of lipids within the cells occurs as a result of an impairment in lipid catabolism, however, not all of the available data are consistent with this theory. In light of this, other mechanisms to explain the etiology of this lipidosis are discussed. Associated with the increase in lipid content within the cell, striking morphological, biochemical and functional changes occur to the alveolar macrophage. Available data indicate that afflicted cells have an increased phagocytic activity and exhibit enhanced killing of one strain of bacteria. While these data suggest an enhancement in certain cellular functions, inadequate information presently exists to allow conclusions to be drawn concerning the consequences of this disorder.

Effects of amiodarone administration during pregnancy in Fischer 344 rats.

Amiodarone is a class III anti-arrhythmic compound that is iodinated, cationic and amphiphilic in nature. The clinical use of amiodarone may be associated with various side-effects, including pulmonary and hepatic toxicity. Use of this compound during pregnancy may therefore place the fetus at risk through in utero exposure. This study was designed to observe any gross developmental effects that may be caused by the administration of amiodarone to Fischer 344 rats during pregnancy, investigate the placental transfer of amiodarone and its principal metabolite, desethylamiodarone and determine the levels of amiodarone and desethylamiodarone in the maternal and newborn lung, liver and plasma. To conduct this study, 35 mg/kg of amiodarone was administered daily to pregnant rats for either the last 7 days of pregnancy, the last 14 days of pregnancy, or for the full 22 days of pregnancy. Drug treatment had no effect on the length of gestation or litter size. Maternal weight gain was decreased only when amiodarone was administered during the last 7 days of gestation. The birthweights of the offspring were decreased, however, crown to rump length was unaffected. Both amiodarone and desethylamiodarone accumulated in the offspring through placental transfer. The levels of both compounds were greater in maternal and newborn lung when compared to maternal and newborn liver, respectively. The maternal lung and liver concentrations of both compounds were significantly higher than the respective newborn concentrations. The newborn plasma concentrations of amiodarone and desethylamiodarone were significantly lower than maternal levels indicating that the placenta may not be totally permeable to the two drugs.

Response of alveolar macrophages to amiodarone and desethylamiodarone, in vitro.

Administration of the antiarrhythmic drug amiodarone to humans or animals may result in lung damage. Amiodarone is metabolized to desethylamiodarone and other minor metabolites. Because amiodarone and the metabolites accumulate in the lungs, it is not possible to ascertain the role of each of these compounds in the induction of toxicity. In the present study, we utilized primary cell cultures of rat alveolar macrophages to study the actions of amiodarone and desethylamiodarone individually and in combination. Neither drug species was metabolized by the cells over 42 h in culture thereby permitting assessment of the actions of each. Both drugs induced the formation of lamellar inclusions, indicative of the development of cellular phospholipidosis. Desethylamiodarone appeared to induce formation of the structures in a shorter period of time than did amiodarone, although given adequate exposure, the two drugs produced similar responses. At shorter times of exposure and lower concentrations, desethylamiodarone was more cytotoxic than amiodarone as assessed by the release of lactate dehydrogenase. The two in combination resulted in cytotoxicity that was more than additive. The results of this study indicate that in vitro cultures of alveolar macrophages may be quite useful in studying the role these cells play in the pulmonary toxicity associated with amiodarone therapy. Additionally, this study supports the idea that a significant portion of the toxicity may result from the actions of desethylamiodarone.

Neonatal toxicity in rats following in utero exposure to chlorphentermine or phentermine.

The administration of chlorphentermine (30 mg/kg) to pregnant rats during the last 5 days of gestation resulted in the development of a phospholipidosis in the lungs of the dams. The disorder developed in utero, as the phospholipidosis was evident in the lungs of the neonates when examined at 12 h postpartum. In contrast, a phospholipidosis was not observed in the lungs of the dams or neonates following phentermine treatment (30 mg/kg). Concurrently, neonates of the chlorphentermine-treated dams displayed a significant decrease in body weight in comparison to controls. Between 16 h and 24 h postpartum, 83% of the neonates of chlorphentermine-treated dams died. Cross-fostering and starvation experiments revealed that the lethality was not due to aberrant maternal behavior by the chlorphentermine-treated dams or malnutrition of the neonates. Histological examinations revealed endothelial and septal alterations in the lungs of neonates from chlorphentermine-treated dams. No signs of toxicity, as evidenced by the maintenance of body weight, or lethality were observed in the neonates of the phentermine-treated dams.

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.

Comparison of the interaction of tricyclic antidepressants with human polymorphonuclear leukocytes as monitored by the generation of chemiluminescence.

The interation of imipramine with human polymorphonuclear leukocytes (PMNs) results in a chemiluminescence (CL) response which has been attributed to the electronic excitation of the imipramine molecule resulting from a reaction of the drug with reactive oxygen species. In order to determine what portion of the tricyclic molecule is involved in this reaction, the interaction of other tricyclics with PMNs was monitored by chemiluminescence. It was observed that tricyclic antidepressants having a carbon atom at position 5 of the ring moiety (amitriptyline, for example) did not yield CL with either resting or zymosan-activated PMNs. In fact this group of compounds inhibited the zymosan-induced CL response. However, CL was observed, with both resting and metabolically-activated PMNs, from several tricyclics having a heterocyclic nitrogen at position 5. These included imipramine, desipramine, opipramol and iprindole. Chlorimipramine, which has a chlorine atom at position 3 of the ring system, failed to yield CL with resting or stimulated cells. Similarly, imipramine N-oxide failed to yield CL with resting cells, but enhanced CL was observed with zymosan-activated PMNs. On the basis of these observations it appears that some aspect of the ring moiety, other than just a heterocyclic nitrogen, facilitates a reaction between these molecules and reactive oxygen which culminates in the generation of CL.

Metabolism of amiodarone following intratracheal instillation in hamsters.

Intratracheal instillation of the antiarrhythmic drug amiodarone (AD) in hamsters is an established animal model of AD-induced pulmonary fibrosis. A metabolite of AD, desethylamiodarone (dAD), has also been shown to produce pulmonary fibrosis in this model. It was previously reported that following intratracheal instillation of AD in hamsters, metabolite could not be detected in lung tissue. However, in studies in our laboratory dAD was detected following instillation of AD. The goal of the present study was to monitor the distribution of AD and dAD to lung and liver within 1 h of AD instillation and to investigate the site of AD metabolism. Both AD and dAD were detected in the lung and liver within 5 min of AD instillation; lung and liver concentrations of AD and dAD were also quantified at 30 and 60 min following AD instillation. Incubation of lung and liver microsomes with AD showed that the liver is a probable site of AD metabolism following the intratracheal administration of AD to hamsters.