Inhibition of Human Plasma and Serum Butyrylcholinesterase (EC 3.1.1.8) by {alpha}-Chaconine and {alpha}-Solanine

The purpose of these experiments was to determine the reversibilityof -chaconine and -solanine inhibition of human plasma butyrylcholinesterase(BuChE). For the substrate -naphthylacetate, optimal assay conditionswere 0.50 M sodium phosphate buffer and a substrate concentrationof 3–5 ' 10^–4 M. Dibucaine (1 ' 10^–5 M) indicatedthe usual phenotype for all subjects; -chaconine and -solanineat 2.88 ' 10^–6 M inhibited BuChE about 70 and 50%, respectively.One-and 24-hr incubations at 1 ' 10^–1 M with -chaconine,-solanine, paraoxon, eserine, and ethanol yielded reversibleinhibition with dilution except for paraoxon. Twenty-four-hourdialyses of incubations showed no inhibition except for paraoxon.PAGE enzyme activity gels of 1-and 24-hr incubations also showedno inhibition except for paraoxon. -Chaconine and -solanineare reversible inhibitors of human butyrylcholinesterase. Atestimated tissue levels, -chaconine, -solanine, and solanidineinhibited BuChE 10–86%. In assays which combined -chaconine,-solanine, and solanidine, inhibition of BuChE was less thanadditive. No inhibition of albumin -naphthylacetate esterase(an arylesterase) was noted with any inhibitor. The importanceof these data to adverse toxicological effects of potato alkaloidsis discussed.     

Kinetic Analysis of the Chronology of Patulin- and Gossypol-Induced Cytotoxicity in Vitro

Kinetic analyses of the mechanisms of patulin- and gossypolinduced cellular toxicity in an immortalized rat hepatocytecell line were examined using a battery of vital fluorescencebioassays. Intracellular glutathione (GSH) content and intracellularCa²⁺ ([Ca²⁺]_i) were monitored simultaneously using fluorescentprobes requiring uv excitation (351–363 nm); reactiveoxygen species (ROS) production, mitochondrial and plasma membranepotential, and intracellular pH were monitored simultaneouslywith visible wavelength probes (488 nm). Changes in gap junction-mediatedintercellular communication (GJIC) were monitored using thegap FRAP technique. Cells were exposed to different concentrationsof patulin (0, 1.0, 10, 100, and 1000 µM) or gossypol(0, 1.0, 3.0, and 10 µM). All parameters were monitoreddirectly after addition of toxin for 20 min. The analyses providedthe following chronology of cellular injury caused by patulin:simultaneous suppression of GJIC and GSH depletion ROS generation mitochondrial membrane depolarization simultaneous increasein [Ca²⁺]_i and cytoplasmic acidification depolarization ofplasma membrane. A distinct chronology of gossypol-induced cellularinjury was also identified: simultaneous suppression of GJICand generation of ROS cytoplasmic acidification simultaneouselevation of [Ca²⁺]_i and partial depletion of GSH mitochondrialmembrane depolarization depolarization of plasma membrane.This report indicates the utility of these vital assays as improvedmechanistically based methods for toxicity testing in vitro.     

d-Limonene Induced Hyaline Droplet Nephropathy in {alpha}2u-Globulin Transgenic Mice

d-Limonene is a hyaline droplet inducing agent and producesnephrotoxicity in male rats when the 1,2-epoxide metabolitebinds to 2u-globulin. Mice, which do not synthesize 2u-globulin,are resistant to hyaline droplet nephropathy. In this study,the ability of d-limonene to cause hyaline droplet nephropathyin a transgenic mouse engineered to express 2u-globulin wasevaluated. The C57BL/6-derived mice excreted 0.4 ± 0.1mg 2u-globulin/day, or approximately 16 mg 2u-globulin/kg bodywt. This represents about 30% of the amount excreted by adultmale rats (11.9 ± 1.1 mg/day or approximately 48 mg/kg).Transgenic mice excreted less mouse urinary protein (9.3 ±1.2 mg/day) than normal mice (15.1 ± 1.6 mg/day). Unlikenormal male rats, untreated transgenic mice did not show significantspontaneous hyaline droplet formation. Liver microsomes fromnaive transgenic mice oxidized d-limonene to the cis- and trans-isomersof the 1,2-epoxide, and following oral treatment with [¹⁴C]d-limonenereversible binding of d-limonene equivalents to renal cytosolicproteins was observed. Furthermore, with d-limonene treatment,hyaline droplets were observed in the transgenic mouse kidneys.These droplets, however, were much smaller in size than thoseseen in d-limonene-treated male rats. The accumulation of 2u-globulinin the kidneys of transgenic mice and normal male rats beforeand after d-limonene treatment was analyzed by Western blotting.These results indicated that 2u-globulin was present in thekidneys of the control transgenic mice, despite the lack ofspontaneous hyaline droplet formation. After d-limonene treatment,approximately a three fold increase in 2u-globulin in the transgenicmouse kidney was observed, a response similar in magnitude tothat seen in d-limonene-treated male rats. These results indicatethat expression of 2u-globulin in a species that does not normallydevelop hyaline droplet nephropathy is necessary and sufficientto render that species sensitive to this renal toxicity.     

The Adverse Effects of Oral 2-Mercaptobenzimidazole on Pregnant Rats and Their Fetuses

The effects of oral 2-mercaptobenzimidazole (2-MBI) on pregnantWistar rats were examined. In a preliminary dose-finding study,pregnant rats treated with 2-MBI over Days 7–17 of gestationshowed reduction in maternal thymus weights with compound-relatedmortality at doses40 mg/kg. No adverse effects on fetuses werefound at doses 40 mg/kg. However, anasarca, cleft palate, anddilated lateral ventricles were present in all fetuses fromthe only survivor among the dams treated with 60 mg/kg of 2-MBI.In the teratology study, pregnant rats were treated with 2-MBIat doses of 0, 3.3, 10, and 30 mg/kg during the period of organogenesis(Gestation Days 7–17). In addition, pregnant rats of threegroups were also treated with 60 mg/kg of 2-MBI for 3 or 4 daysduring specific periods of organogenesis (Days 7–10, 11–14,or 15–17 of gestation). Treatment on Gestation Days 7–17resulted in reduced maternal thymus weights at doses of 3.3mg/kg. In addition to reduced fetal weights, visceral variations(kinked ureter and dilated renal pelvis) and delayed ossificationwere seen in the fetuses at doses 10 mg/kg, and skeletal variations(rudimentary lumbar ribs) were seen at 30 mg/kg. In the fetusesfrom the dams treated with 60 mg/kg of 2-MBI, rudimentary lumbarribs were seen mainly in the group treated on Days 7/10 of gestation,whereas kinked ureter and dilated renal pelvis were evidentmainly in the group treated on Gestation Days 15/17. Dilatedlateral ventricles and cleft palate were present only in thegroup treated with 60 mg/kg on Days 11–14 of gestation,though 5 out of 16 dams died during the study. In conclusion,maternal toxicity preceded fetal toxicity and major fetal malformationswere seen only at a dose (60 mg/kg) which was lethal to manyof the treated dams.     

Development of a Mechanism-Based Dosimetry Model for 2,4,4-Trimethyl-2-pentanol-lnduced {alpha}2u-Globulin Nephropathy in Male Fischer 344 Rats

A mechanism-based dosimetry model was developed to describe2,4,4-trimethyl-2-pentanol (TMP-2-OH) dosimetry and renal 2u-globulin(2u) nephropathy in the male Fischer 344 rat. Experimental datawere collected to estimate the chemical-specific parameters(metabolic constants, tissue solubility, and oral absorptionrate) necessary to describe TMP-2-OH dosimetry in male rats.The concentrations of 2u and TMP-2-OH were measured in malerats up to 64 hr after a single oral dose of TMP-2-OH (6, 60,or 600 mg/kg). The model predicted the time course behaviorof TMP-2-OH and 2u in the kidney, but overestimated their renalconcentrations by two or threefold. Simulations of renal 2uconcentration were sensitive to changes in TMP-2-OH-2u-bindingaffinity and degradation rate of the TMP-2-OH-protein complex.In contrast, simulation of the concentration of TMP-2-OH inthe kidney was most sensitive to the amount of protein present.Oral absorption of TMP-2-OH was dose dependent. The model predictedthat 2u and TMP-2-OH concentration in the kidney is sensitiveto changes in the rate of TMP-2-OH absorbed after oral administration.This model permitted a more rigorous evaluation than has previouslybeen possible of the combination of protein characteristicsand chemical dosimetry required for the accumulation of 2u inthe kidney of male rats. The behavior of the model is consistentwith the qualitative aspects of the 2u hypothesis. However,further characterization of 2u distribution and renal hydrolysiswill be required in order to fully characterize the hypothesisat the quantitative level.     

Application of Molecular Encapsulation for Toxicology Studies: Comparative Toxicity of p-Chloro-{alpha},{alpha},{alpha}-trifluorotoluene in {alpha}-Cyclodextrin Vehicle versus Corn Oil Vehicle in Male and Female Fischer 344 Rats and B6C3F1 Mice

The application of -cyclodextrin (-CD) as an alternative vehiclefor water insoluble and volatile chemicals was investigatedin toxicity studies of p-chloro-,,-trifluorotoluene (CTFT).Groups of F344 rats and B6C3F1 mice of each sex were administeredCTFT (97% pure) by gavage in either corn oil or -CD aqueousformulations daily for 14 consecutive days. The dose levelsused were 10 (mice only), 50, 400, and 1000 mg/kg for corn oilvehicle and 10, 50, and 400 mg/kg (maximum achievable dose atgavage volume of 5 ml/kg) for -CD vehicle. With both vehiclesCTFT and a_2u-globulin were found to accumulate in the male ratkidney after 14 days of exposure and a dose-related toxic nephropathywas observed at dose of 50 mg/kg or higher. The hepatocellularhypertrophy and cytoplasmic vacuolation of the adrenal cortexwhich appeared in dosed male and female rats were also foundto be independent of vehicle. Clinical pathology findings suggesteda mild anemia and cholestasis in rats. With both vehicles notissue bioaccumulation of CTFT was found in male or female mice.Vehicle-independent hepatocellular hypertrophy and cholestasiswere also observed in mice at doses of 400 and 1000 mg/kg. Inconclusion, the -CD vehicle does not affect the toxic responsesof CTFT in both sexes of both species. The results of the studiessuggest that -CD may be an appropriate alternative vehicle fortoxicity studies.     

NCI-Black-Reiter (NBR) Male Rats Fail to Develop Renal Disease following Exposure to Agents That Induce {alpha}-2u-Globulin ({alpha}2u) Nephropathy

NCI-Black-Reiler (NBR) Male Rats Fail to Develop Renal Diseasefollowing Exposure to Agents That Induce _2u-Globulin (_2u) Nephropathy.Dietrich, D. R., and Swenberg, J. A. (1991). Fundam. Appl. Toxicol16, 749–762. The NCI-Black-Reiter (NBR) rat is the onlystrain of male rat known not to synthesize the hepatic formof the low molecular weight protein, _2u-globulin. In previousstudies, NBR rats were shown not to develop renal disease whenexposed to decalin, a compound known to induce _2u-globulin nephropathyin other rat strains. The objective of this study was to showthat the presence of _2u-globulin (_2u-) is essential for thedevelopment of this syndrome in rats exposed to 2,2,4-trimethylpentane(TMP), 1,4-dichlorobenzene (DCB), isopho-rone (IP), PS-6 unleadedgasoline (UG), and d-limonene (d-L). The induction of _2u-nephropathyin F344 male rats with lindane was used as a positive controland this response was contrasted to male NBR and female F344rats treated with lindane. Five to seven 11-week-old male NBRrats were exposed to TMP (500 mg/kg/day), DCB (500 mg/kg/day),IP (1000 mg/kg/day), UG (500 mg/kg/day), d-L (1650 mg/kg/day),or lindane (10 mg/kg/day) and five 11-week-old male and femaleF344 rats were exposed to lindane (10 mg/kg/day) by oral gavageon 4 consecutive days. NBR male and F344 male and female ratsgavaged with corn oil were incorporated in the study as vehiclecontrols. The presence of hyaline droplets was assessed in perfusion-fixedkidneys by staining paraffin sections with Mallory-Heidenheinstain and in GMA sections with Lee's methylene basic blue fuchsinstain. Paraffin sections were also analyzed immunohistochemicallyfor the presence of _2u-. Under exposure conditions that clearlyinduce _2u-nephropathy in male F344 rats, no lesions, hyalinedroplets, or _2u- were detectable in treated or control maleNBR and female F344 rats. It is thus concluded that the presenceof _2u is causal to the development of renal disease in ratsexposed to TMP, DCB, IP, UG, d-L, and lindane.     

Pulmonary and Pleural Responses in Fischer 344 Rats Following Short-Term Inhalation of a Synthetic Vitreous Fiber: I. Quantitation of Lung and Pleural Fiber Burdens

The pleura is an important target tissue of fiber-induced disease,although it is not known whether fibers must be in direct contactwith pleural cells to exert pathologic effects. In the presentstudy, we determined the kinetics of fiber movement into pleuraltissues of rats following inhalation of RCF-1, a ceramic fiberpreviously shown to induce neoplasms in the lung and pleuraof rats. Male Fischer 344 rats were exposed by nose-only inhalationto RCF-1 at 89 mg/m³ (2645 WHO fibers/cc), 6 hr/day for 5 consecutivedays. On Days 5 and 32, thoracic tissues were analyzed to determinepulmonary and pleural fiber burdens. Mean fiber counts were22x10⁶/lung (25x10³/pleura) at Day 5 and 18x10⁶ (16x10/pleura)at Day 32. Similar geometric mean lengths (GML) and diameters(GMD) of pulmonary fiber burdens were observed at both timepoints. Values were 5 µm for GML (geometric standard deviationGSD 2.3) and 0.3 µm for GMD (GSD 1.9), with correlationsbetween length and diameter () of 0.2–0.3. Size distributionsof pleural fiber burdens at both time points were approximately1.5 µm GML. (GSD 2.0) and 0.09 µm GMD (GSD 1.5; 0.2–0.5). Few fibers longer than 5 µm were observedat either time point. These findings demonstrate that fiberscan rapidly translocate to pleural tissues. However, only short,thin (<5 µm in length) fibers could be detected overthe 32-day time course of the experiment.     

Difference in the Developmental Toxicity of Ethylenethiourea and Three N,N'-Substituted Thiourea Derivatives in Rats

Difference in the Developmental Toxicity of Ethylenethioureaand Thm N,N'-Substituted Thiourea Derivatives in Rats. SAILLENFAIT,A. M., SABATE, J. P., LANGONNE, I., AND DE CUURRIG J. (1991).Fundam. Appl Toxicol 17, 399–408. Sprague-Dawley ratswere administered ethylenethiourea (ETU), 1,3-dimethyl-2-thiourea(DMT), 1,3-dibutyl-2-thiourea (DBT), or 1,3-diphenyl-2-thiourea(DPT) by gavage from Days 6 to 20 of gestation. Daily dosagelevels (mg/kg/day) were ETU at 0, 15, 25 and 35; DMT at 0, 15,25, 50, 100, and 200; DBT at 0, 15,25, 50, 100, and 200; andDPT at 0,25, 50, 100, and 200. There was evidence of maternaltoxlcity at all doses of DMT and at doses 50 mg DBT/kg/day.DPT was embryolethal at 200 mg/kg/day. Fetotoxicity was observedat doses 15 mg DMT/kg/day, 15 mg DBT/kg/day, and 100 mg DPT/kg/day.ETU was the only chemical tested that proved to be teratogenic.     

Prechronic Inhalation Toxicity Studies of Isobutyl Nitrite

Isobutyl nitrite (IBN) is a volatile liquid that has becomeincreasingly popular as an inhaled recreational drug. To investigateshort-term toxic effects and establish exposure parameters forchronic inhalation studies, F344/N rats and B6C3F1 mice wereexposed to IBN vapors on a 6 hr/day + t90, 5 days/week schedule.Twelve exposures were administered at concentrations of 0, 100,200, 400, 600, and 800 ppm IBN. This exposure series resultedmortality in rats exposed to 600 ppm and mice exposed to 800ppm. Animals exposed at the lower concentrations developed hyperplasiaof the bronchiolar and nasal turbinate epithelium (rats andmice) and lymphocytic atrophy in the spleen and thymus (mice).Longer term, 13-week, subchronic exposures were conducted atconcentrations of 0, 10, 25, 75, 150, and 300 ppm IBN. Exposureto 300 ppm IBN reduced the body weight gains in both sexes ofrats and in female mice. IBN-related clinical pathology changesincluded reduced RBC counts accompanied by moderate increasesin mean corpuscular volume and reticulocyte counts, increasedWBC counts, and mildly increased methemoglobin concentration.Bone marrow hyperplasia was observed in all groups of IBN-exposedrats, while in mice only females at l50 ppm IBN displayed thischange. Excessive splenic pulp hematopoiesis was noted in miceat all IBN exposure levels. Respiratory system changes includedincreased lung weights in rats and female mice at 300 ppm, hyperplasiaof the nasal mucosa (male rats at 75 ppm and female rats at150 ppm), and hyperplasia of the lung epithelium (male miceat 150 ppm and female mice at 75 ppm). The results suggestedthat a concentration of 150 ppm could be used as the highestexposure level for subsequent chronic inhalation tests.     

Neuropharmacologic and Neuropathologic Effect of Fenvalerate in Mice and Rats

Neuropharmacologic and Neuropathologic Effect of Fenvaleratein Mice and Rats. PARKER, C.M., ALBERT, J.R., VAN GELDER, G.A.,PATTERSON, D.R., and TAYLOR, J. L. (1985). Fundam. Appl. Toxicol.5, 278–286. B6C3F1 mice and Sprague-Dawley rats displayedthe characteristic signs of pyrethroid intoxication followingsingle oral doses ranging from 56 to 320 and 133 to 1000 mg/kgfenvalerate, respectively. The LD50s for mice and rats were180 and 776 mg/kg, respectively, with corn oil as the vehicle.Signs of neurologic deficit such as splayed gait, tremors, ataxia,and hind limb incoordination were observed at doses of 100mg/kg (mice) and 133 mg/kg (rats) within 1–8 hr afterdosing. These signs had disappeared in most animals within 72hr. Slight peripheral nerve fiber damage was detected in survivingmice and rats sacrificed 10 days after dosing. The incidenceand severity were dose related at doses 56 and 180 mg/kg; however,even at lethal doses, evidence was lacking for the presenceof nerve lesions in several animals. Thus two distinct neurologiceffects were observed: a reversible ataxia/incoordination anda neuropathologic effect manifested as sparse axonal damagein peripheral nerve.     

Development of Fish Peritoneal Macrophages as a Model for Higher Vertebrates in Immunotoxicological Studies: I. Characterization of Trout Macrophage Morphological, Functional, and Biochemical Properties

Development of Fish Peritoneal Macrophages as a Model for HigherVertebrates in Immunotoxicological Studies. I. Characterizationof Trout Macrophage Morphological, Functional, and BiochemicalProperties. ZELIKOFF, J. T., ENANE, N. A., BOWSER, D., SQUIBB,K. S., AND FRENKEL, K. (1991). Fundam. Appl. Toxicol. 16, 576–589.The immune defense mechanisms of fish are not as well characterizedas those of mammals but seem to be related and similarly competent.Because of this, there is an increased interest in the immuneresponses of fish as models for higher vertebrates in immunotoxicologicalstudies. Prior to such studies, baseline criteria for specificcomponents of the immune response needed to be established.For this study, we have examined trout macrophage morphologyusing light and scanning electron microscopy, phagocytic activity,random and stimulus-directed migration, and superoxide anionradical (^{dot}) production for resident and lipopolysacharide (LPS) or Aeromonas salmonicidae-elicited rainbowtrout (Oncorhynchus mykiss) peritoneal macrophages (M). Followingperitoneal lavage, >89% of the cells were M as determinedby differential counts and nonspecific esterase staining. Immunizationwith LPS and A. salmonicidae increased M number {small tilde}5and 13-fold, respectively, and overall size. Trout M were phagocyticallyactive engulfing serum opsonized latex particles and were mobile,migrating both randomly and in a directed fashion towards formyl-methionine-L-leucine-L-phenylalanine(FMLP) and trout serum-derived complement fragment C5a. Concentrationsof FMLP (100 nM) and C5a (0.01–1%) effective for attractingtrout M are the same as those used to attract rabbit M. Residenttrout M produced negligable quantities of-(^{dot}) following stimulation with 1 µg/ml phorbol myristate acetate;Aeromonas-elicited M produced (^{dot}) in a time-dependen manner which peaked after 60 min at 2.9 nmolper 2 ? 10₅ cells and then declined. The results of this studyprovide a data base for future toxicological studies with troutperitoneal M and indicate the usefulness of this system forimmunotoxicological studies.     

Toxicity and Carcinogenicity of {Delta}9-Tetrahydrocannabinol in Fischer Rats and B6C3F1 Mice

⁹-Tetrahydrocannabinol (⁹-THC) was studied for potential carcinogenicityin rodents because it is the principal psychoactive ingredientin marihuana and it has potential medicinal uses. ⁹-THC in cornoil was administered by gavage to groups of male and femaleFischer rats and B6C3F1 mice at 0, 5, 15, 50, 150, or 500 mg/kg,5 days a week for 13 weeks and for 13-week plus a 9-week recoveryperiod, and to groups of rats at 0, 12.5, 25, or 50 mg/kg andmice at 0, 125, 250, or 500 mg/kg, 5 times a week for 2 years.In all studies, mean body weights of dosed male and female ratsand mice were lower than controls but feed consumptions weresimilar. Convulsions and hyperactivity were observed in dosedrats and mice; the onset and frequency were dose related. SerumFSH and LH levels hi all dosed male rats and corticosteronelevels in 25 mg/kg female rats were significantly higher thancontrols at 15 months in the 2-year studies. ⁹-THC administrationfor 13 weeks induced testicular atrophy and uterine and ovarianhypoplasia; the lesions persisted in a 9-week recovery period.In the 2-year studies, survival of dosed rats was higher thancontrols; that of mice was similar to controls. Incidences oftesticular interstitial cell, pancreas and pituitary gland adenomasin male rats, mammary gland fibroadenoma and uterus stromalpolyp in female rats, and hepatocellular adenoma/carcinoma inmale and female mice were reduced in a dose-related manner.Decreased tumor incidences may be at least in part due to reducedbody weights of dosed animals. Incidences of thyroid gland follicularcell hyperplasia were increased in all dosed groups of maleand female mice, and follicular cell adenomas were significantlyincreased in the 125 mg/kg group of males, but there was noevidence of a dose-related trend in proliferative lesions ofthe thyroid. There was no evidence that ⁹-THC was carcinogenicin rats or mice.     

Differences in the Mode of Lethality Produced through Intravenous and Oral Administration of Organophosphorus Insecticides in Rats

Differences in the Mode of Lethality Produced through Intravenousand Oral Administration of Organophosphorus Insecticides inRats. TAKAHASHI, H., KOJIMA, T., IKEDA, T., TSUDA, S. and SHIRASU,Y. (1991). Fundam. Appl. Toxicol. 16, 459–468. This studywas undertaken to investigate the possibility that mechanismsother than cholinesterase (ChE) inhibition account for the acutetoxicity of organophosphorus insecticide. Both the PO type insecticide(direct ChE inhibitors: chlorfenvinphos and dichlorvos) andthe PS type insecticide (indirect ChE inhibitors: diazinon andfenthion) were employed. Rats treated with lethal doses of intravenousand oral PO type insecticides and oral PS type insecticidesexhibited typical signs of anti-ChE poisoning along with markedinhibition of brain and erythrocyte ChE activity. In contrast,rats given lethal doses of intravenous PS type insecticidesexhibited tonic convulsions and opisthotonos, with only slightinhibition of ChE activities. When PO type insecticides wereintravenously administered to anesthetized and conscious rats,animals exhibited typical anti-ChE poisoning signs in cardiorespiration:hypertension and apnea which were antagonized by atropine. Afteradministration of lethal doses of PO type insecticides, breathingdisappeared before the cessation of heart beats. Rats receivinglethal doses of intravenous PS type insecticides did not showhypertension, but exhibited transient cessation of breathingand heart beats. Breathing was observed after the disappearanceof heart beats. The electroencephalogram (EEG) was characterizedby spike and wave complexes. The EEG and cardiorespiratory changeswere not antagonized by atropine. It was concluded that lethalityfollowing intravenous PS type insecticides may be independentof ChE inhibition.     

Organ-Specific Hematopoietic Changes Induced by a Recombinant Human Interferon-{alpha} in Mice

Organ-Specific Hematopoietic Changes Induced by a RecombinantHuman Interferon- in Mice. ROSENTHAL, G. J., STRANAHAN, R. P.,ILL, THOMPSON, M., BLAIR, P., GERMOLEC, D. R., COMMENT, C. E.,SCHWAB, K., AND LUSTER, M. I. (1990). Fundam. Appl. Toxicol.14, 666–675. Interferon-a (IFN-) is a naturally occurringcytokine that mediates numerous biological activities and hasdemonstrated therapeutic potential in a variety of malignancies.Encouraging activity against HIV-1 replication has also beenobserved with IFN- in the treatment of AIDS, although hematotoxicityhas been a frequently observed side effect. In addition, invitro studies have suggested that IFN- may function as a down-regulatorof myelopoiesis. A recombinant hybrid of subtypes of human IFN-,rHuIFN-A/D, has antiviral activity in mu-rine cells in vitroand In vivo. This study examines the effect of acute and subchronicexposure to rHuIFN-A/D on hemopoietic and immune parametersin C57B1/6 mice. IFN-a was administered ip at 0, 1000, 10,000,and 100,000 units/day for either 1 or 10 consecutive days. Manyof the known effects of IFN- in humans such as anemia, leukopenia,and thrombocytopenia were observed in mice following subchronicexposure, with the latter two effects also manifested followingacute exposure. Further analysis showed that this leukopeniawas not selective. Both splenic and bone marrow cells were examinedfollowing 10 days of dosing with the high dose of IFN-. Lymphocyteswere reduced in both compartments, while granulocytes were increasedin both compartments. Bone marrow cells programmed to differentiateinto granulocytes (CFU-G) were suppressed, while macrophageprogenitors (CFU-M) were stimulated. Erythroid cells decreasedin the marrow but increased in the spleen, suggesting that themicroenvironmerit may play a significant role in the effectof IFN-. The proliferative capacity of both B and T spleniclymphocytes was significantly suppressed in a dose-related fashionfollowing multiple exposure to IFN-a. Clinically, IFN-a is mostoften given in multiple doses and the present data suggest thatsuch a regimen is toxic to both erythroid and myeloid cells,as well as being immunotoxic to splenic B and T lymphocytes.     

Hepatic and Adrenal Toxicity of a Novel Lipid Regulator in Beagle Dogs

PD 138142-15 is a substituted urea hypolipidemic and potentialanti-atherosclerotic agent. To determine the toxicity of PD138142-15, beagle dogs were given oral doses of 1, 10, 30, and100 mg/kg daily for 13 weeks. Two animals at 100 mg/kg wereeuthanized during Week 5 due to poor condition. Clinical findingsincluded decreased serum albumin at mg/kg, and increased ALP(up to 30-fold) and 5'-nucleotidase activities (up to 9-fold)at doses 10 mg/kg. ALT and AST activities were elevated onlyat 100 mg/kg. There was a two- to threefold increase in cytochromeP450 content of hepatic microsomes from all treated animalsand increases in liver weights at 10 mg/kg and above. Hepaticchanges included hepatocellular hypertrophy and increased cytoplasmiceosinophilia at 10 mg/kg; single cell necrosis of hepatocyteswas noted in moribund animals. ACTH-stimulated cortisol levelswere decreased at 30 and 100 mg/kg. Adrenal cholesterol esterswere decreased at 10 mg/kg and above, while total adrenal cholesterolwas decreased at 30 mg/kg. These changes correlated with adrenalcortical zonal atrophy, principally of the zona fasciculataand zona reticularis, present at 30 and 100 mg/kg. Plasma concentrationsof PD 138142-15 increased with increasing dose; plasma levelswere significantly lower during Week 12 than those on Day 1,possibly due to autoinduction. Overt hepatotoxicity occurredat 100 mg/kg, whereas hepatic changes at 10 and 30 mg/kg wereconsistent with cytochrome P450 induction. The hepatic lesionswere reversible within 4 weeks, while adrenal lesions were stillevident after 4 weeks without treatment.     

The Perturbation of Hepatic Glutathione by {alpha}2-Adrenergic Agonists

The Perturbation of Hepatic Glutathione by ₂ -Adrenergic Agonists.James, Robert C, Roberts, Stephen M. and Harbison, Raymond D.(1983). Fundam. Appl. Toxicol.. 3: 303–308. Single injectionsof epinephrine significantly lowered the hepatocellular levelsof reduced glutathione (GSH) while producing small but significantelevations in serum glutamic-pyruvic transaminase (SGPT) activity.Hormones, i.e. glucagon and the corticosteroids, were also foundto depress significantly hepatic glutathione. Based upon theagonist-antagonist studies performed, the hepatic GSH loweringeffects of epinephrine appear to be mediated solely by ₂ receptors.Adrenergic antagonists with ₂ receptor blocking properties,phenotolamine and yohimbine, prevented the epinephrine-inducedlowering of GSH while agonists with ₂ activity, clonidine andguanabenz, mimicked epinephrine's response. Antagonists witheither ₁or ß activity, i.e. prazosin, phenoxybenzamineand propranolol, did not prevent the epinephrine-induced loweringof hepatic GSH. Contrary to these findings antagonists witheither or P receptor blocking activity significantly reducedthe epinephrine-induced elevations in SGPT activity. Thus, therewas no apparent relationship between the elevation of SGPT activityand the reduction in hepatic glutathione levels. It is concludedthat the therapeutic administration of these compounds, or physiologicresponses to stress or pain, may exacerbate the hepatotoxicityof compounds detoxified by GSH or alter important glutathione-mediatedhepatocellular processes.