Toxicological assessment of gadoversetamide injection (OptiMARK), a new contrast-enhancement agent for use in magnetic resonance imaging.

RATIONALE AND OBJECTIVES: A series of preclinical tests were undertaken during the developmental process to determine the safety profile of gadoversetamide injection (OptiMARK). METHODS: Acute intravenous, acute intracisternal, and repeated-dose toxicities; cardiovascular effects; and genetic and reproductive toxicology characteristics were assessed in several animal species. RESULTS: Gadoversetamide injection demonstrated an acute intravenous median lethal dose of 25 to 28 mmol/kg and a maximum nonlethal dose of 14 mmol/kg in mice. In the dog, acute administration of gadoversetamide injection showed a no observable effect level at 3 mmol/kg. Dosed daily for 4 weeks, gadoversetamide injection (0.1 mmol x kg(-1) x d(-1)) caused no serious irreversible changes in any organs in rats and dogs. At a dose of 0.1 mmol/kg, gadoversetamide injection caused no significant (P < 0.05) changes in cardiovascular function in anesthetized dogs. Gadoversetamide injection showed no mutagenic activity. Fertility, reproductive performance, and postnatal fetal development were not affected at doses up to 0.5 mmol x kg(-1) x d(-1) in the rat. No teratogenicity was observed at doses up to 4.2 mmol x kg(-1) x d(-1) in the rat and up to 1.6 mmol x kg(-1) x d(-1) in the rabbit. CONCLUSIONS: Data from our toxicological assessment demonstrate the safety of gadoversetamide injection in a number of animal species at doses exceeding the intended human clinical dose.

Developmental toxicity evaluation of inhaled toluene diisocyanate vapor in CD rats.

Mated female CD (Sprague-Dawley) rats, 25/group, were exposed to toluene diisocyanate (TDI) vapor, for six h/day on gestational days (gd) 6 through 15, at 0.00, 0.02, 0.10, or 0.50 p.p.m.. Maternal clinical signs, body weights, and feed and water consumption were recorded throughout gestation. At termination (gd 21), maternal body, gravid uterine, and liver weights were recorded. Corpora lutea were counted, and implantation sites were identified: resorptions and dead and live fetuses. All live fetuses were examined for external alterations. One-half of the live fetuses/litter were examined for visceral (including craniofacial) alterations. The remaining intact fetuses/litter were stained with alizarin red S and examined for ossified skeletal alterations. Maternal toxicity at 0.50 ppm consisted of reduced body weights, body weight gains, feed consumption, and clinical signs of toxicity. Water consumption was unaffected. Gestational parameters exhibited no significant treatment-related changes, including pre- and postimplantation loss, sex ratio/litter, or fetal body weights/litter. Incidences of individual malformations, malformations by category (external, visceral, and skeletal), total malformations, individual external and visceral variations, variations by category, and total variations were unaffected. Of 111 skeletal variants observed, only 1, incidence of poorly ossified cervical centrum 5, was increased at 0.50 ppm, indicating possible minimal fetotoxicity, although it occurred in the absence of any other indications of developmental toxicity. Therefore, exposure to TDI vapor by inhalation, during major organogenesis in CD rats, resulted in maternal toxicity and minimal fetotoxicity at 0.50 ppm no observed adverse effect level (NOAEL) for maternal and developmental toxicity was 0.10 ppm. No treatment-related embryotoxicity or teratogenicity was observed.

Two-week aerosol inhalation study on polyethylene glycol (PEG) 3350 in F-344 rats.

PEGs in the 3000 to 4000 MW range are used in many pharmaceutical and cosmetic applications; they produce little ocular or dermal irritation and have extremely low acute and subchronic toxicity by oral and dermal routes of administration. However, little information exists on the potential of aerosols of these materials to produce adverse health effects. F-344 rats were exposed to aerosols of PEG 3350 (20% w:w in water) at 0, 109, 567, or 1008 (highest attainable) mg/m3 for 6 hr/d, 5 d/wk for 2 wk. No exposure-related toxicity was found with regard to clinical signs, ophthalmology, serum chemistry, urinalysis, or gross pathology. Exposure-related effects included: a 50% increase in the neutrophil count (males only) at 1008 mg/m3; decreased body weight gain (16%) for both the 567 and 1008 mg/m3 groups (males only); absolute lung weights of both sexes were increased 10 and 18% for the 567 and 1008 mg/m3 groups, respectively. A slight increase in the number of macrophages in the alveoli was the only change observed histologically in all PEG 3350-exposed groups. Therefore, inhalation of aerosols of PEG 3350 at concentrations up to 1008 mg/m3 produced relatively little toxicity in rats, the lung was the target organ, and the no-observable-effect-level was between 109 to 567 mg/m3.

Corneal dystrophy in Fischer 344 rats.

A spontaneous degenerative lesion of the cornea resembling calcific band keratopathy in man has been observed in 10-15% of the F-344 rats (aged 35-300 days) purchased from a private vendor's closed breeding colony. The lesion appears clinically as punctuate to linear superficial corneal opacities located in the interpalpebral fissure of one or both eyes. Occasional roughening, bleb formation, or pitting of the corneal surface resembling superficial ulcers may be observed. The lesion occurs in both sexes. It is rarely associated with inflammation or irritation. Histologically, it consists of mineral deposits along the epithelial basement membrane and Bowman's space, some of which are large enough to disrupt or destroy portions of the basilar epithelium. Energy dispersive X-ray analysis of the deposits proved them to be composed of calcium and phosphorus. Electron microscopic examination revealed a variety of extracellular laminated and crystalline arrays similar to those seen in humans with band keratopathy. The etiology of the lesion is as yet undetermined. A genetic-associated susceptibility due to hypercalcemia may be involved.

Pulmonary fibrosis produced in F-344 rats by subchronic inhalation of aerosols of a 4000 molecular weight ethylene oxide/propylene oxide polymer.

Inhalation of aerosols of the ethylene oxide/propylene oxide polymer (U-5100) evaluated in this study has previously been shown in acute and 2-week studies to produce toxicologic effects on the lungs, with increased lung weights and microscopic findings of congestion and hemorrhage of pulmonary alveolar capillaries and necrosis of alveolar epithelial cells (D. R. Klonne, D.J. Nachreiner, D. E. Dodd, P. E. Losco, and T.R. Tyler, 1987, Fundam. Appl. Toxicol. 9, 773-784). In the present studies, F-344 rats were exposed 6 hr/day, 5 day/week for 2 weeks to aerosols at mean concentrations of 0, 0.9, or 5.0 mg/m3 or for 13 weeks to mean concentrations of 0, 0.3, 1.1, or 5.2 mg/m3. Following the 2-week study, minimal multifocal hemorrhage and eosinophilic proteinaceous debris in alveoli were observed in the 0.9 mg/m3 group; similar lesions plus alveolar cell necrosis were found in the 5 mg/m3 group. In the 13-week study, the 5.2 mg/m3 group had a slight decrease in body weight gain, while increases in absolute and/or relative lung weights occurred for both the 1.1 and 5.2 mg/m3 groups at the end of the exposure regimen and at the end of a 5-week recovery period. Histologic lesions of the lungs occurred in all U-5100-exposed groups and consisted of hemorrhage, alveolar histocytosis, interstitial pneumonia, and multifocal fibrosis. The incidence and severity of the pulmonary lesions were concentration related.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyalin droplet nephrosis in male Fischer-344 rats following inhalation of diisobutyl ketone.

Four groups, each consisting of 10 male and 10 female Fischer-344 rats, were exposed 6 h/day, 5 days/week, for 9 days to diisobutyl ketone (DIBK) vapor at concentrations of 905, 300, 98, or 0 (control) ppm. An additional 10 rats/sex were assigned to the 905 and 0 ppm groups and allowed two weeks recovery prior to sacrifice. Rats exposed to 905 ppm had mild ocular irritation (lacrimation) and evidence of kidney toxicity, manifested as: 1) an increase in absolute and relative (as a percentage of body weight) kidney weights, 2) an increase in urine volume (and water intake) with a concomitant decrease in urine osmolality (males only), and 3) an increase in severity of hyalin droplet nephrosis in the proximal tubules (males only). Absolute and relative liver weights were also increased in both male and female rats of the 905 and 300 ppm groups. These effects either disappeared or lessened in severity following the 2-week recovery period. Male rats exposed to 300 ppm had similar renal alterations to the males of the 905 ppm group, although the alterations were fewer in number and smaller in magnitude. Kidney weights and renal histology of the males of the 98 ppm group were similar to the control male rats, although an increase in urine volume with a decrease in urine osmolality was observed. The kidney findings in this study were not surprising because of the chemical relationship of DIBK with other aliphatic ketones (e.g., methyl isobutyl ketone, methyl isoamyl ketone) which, after repeated inhalation exposure, cause hyalin droplet nephropathy in male rats. The significance of this male rat nephrosis with regard to human exposure is unknown.

Dimethylethanolamine: acute, 2-week, and 13-week inhalation toxicity studies in rats.

Dimethylethanolamine (DMEA) is a volatile, water-soluble amine that has applications in the chemical and pharmaceutical industries. These studies evaluated the acute and subchronic inhalation toxicity of DMEA. Acute (4-hr) exposures of Wistar rats to DMEA vapor resulted in an LC50 value (95% confidence limits) of 1641 (862-3125) ppm. Clinical signs of nasal and ocular irritation, respiratory distress, and body weight loss were observed in rats exposed to 1668 ppm DMEA and higher. In the 2-week study, F-344 rats exposed to 98, 288, or 586 ppm DMEA for 9 days (6 hr/day) during an 11-day period also exhibited signs of respiratory and ocular irritation (except the 98 ppm group). All animals of the 586 ppm group and 4 of 15 male rats of the 288 ppm group died. Body weight values for the 288 ppm group were reduced to about 75% of preexposure values, while the 98 ppm group gained 35% less weight than controls. Statistically significant differences in clinical pathology parameters (288 ppm group) and in organ weight values (288 and 98 ppm groups) probably resulted from the decreased food consumption and not from specific target organ toxicity. In the groups evaluated histologically (the 98 and 288 ppm groups) the eye and nasal mucosa were the primary target organs. In the 13-week subchronic study, F-344 rats were exposed to 0, 8, 24, or 76 ppm DMEA for 6 hr/day, 5 days/week for 13 weeks. The principal exposure-related changes were transient corneal opacity in the 24 and 76 ppm groups; decreased body weight gain for the 76 ppm group; and histopathologic lesions of the respiratory and olfactory epithelium of the anterior nasal cavity of the 76 ppm group and of the eye of several 76 ppm group females. Rats maintained for a 5-week recovery period only exhibited histological lesions of the nasal tissue, with the lesions being decreased in incidence and severity. DMEA acts primarily as an ocular and upper respiratory tract irritant and toxicant at vapor concentrations of 76 ppm, while 24 ppm or less produced no biologically significant toxicity in rats. Thus, 24 ppm was considered to be the no-observable-effect level.

Biological effects of short-term, high-concentration exposure to methyl isocyanate. I. Study objectives and inhalation exposure design.

Early reports from India indicated that humans were dying within minutes to a few hours from exposure to methyl isocyanate (MIC). Attempts to explain the cause(s) of these rapid mortalities is where Union Carbide Corporation concentrated its post-Bhopal toxicologic investigations. The MIC studies involving rats and guinea pigs focused primarily on the consequences of acute pulmonary damage. All MIC inhalation exposures were acute, of short duration (mainly 15 min), and high in concentration (ranging from 25-3506 ppm). MIC vapors were statically generated in a double chamber exposure design. Precautionary measures taken during exposures are discussed. Guinea pigs were more susceptible than rats to MIC exposure-related early mortality. A greater than one order of magnitude difference was observed between an MIC concentration that caused no early mortality in rats (3506 ppm) and an MIC concentration that caused partial (6%) early mortality in guinea pigs (225 ppm) for exposures of 10 to 15 min duration. For both species, the most noteworthy clinical signs during exposure were lacrimation, blepharospasm, and mouth breathing. Fifteen minute LC50 tests with 14-day postexposure follow-up were conducted, and the LC50 (95% confidence limit) values were 171 (114-256) ppm for rats and 112 (61-204) ppm for guinea pigs. Target exposure concentrations for the toxicologic investigations of MIC-induced early mortality were established. A short summary of pertinent results of Union Carbide Corporation's post-Bhopal toxicologic investigations is presented.

Biological effects of short-term, high-concentration exposure to methyl isocyanate. VI. In vitro and in vivo complement activation studies.

The ability of MIC to induce complement activation in vitro and in vivo was investigated. For the in vitro studies, both human and guinea pig serum or EDTA-plasma samples were exposed to 1167 to 1260 ppm MIC vapor for 15 min at room temperature. The human serum samples exposed to MIC showed significant reductions in Factor B, C2, C4, C3, C5, and total hemolytic complement CH50 activity levels. C6 functional activity was unaffected. The C3, C5, and CH50 functional activities in guinea pig serum (the only functional tests conducted on these samples) were more sensitive to MIC-mediated reduction than the corresponding activity reductions observed in the human serum samples. The human and single guinea pig EDTA-plasma samples exposed to MIC vapor showed no evidence of C3 consumption but did show significant reductions in CH50 levels. Thus, MIC vapor was able to activate, and thereby reduce serum complement C3 activity in vitro by a complement-dependent process. However, the data suggest at least one complement component other than C3 was inactivated in EDTA-plasma by a complement-independent mechanism. For the in vivo studies, five pairs of guinea pigs were exposed to 644 to 702 ppm MIC vapor until one of the pair died (11-15 min). MIC exposure was then discontinued, the surviving guinea pig was sacrificed, and EDTA-plasma was obtained from both animals and analyzed for complement consumption.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological effects of short-term, high-concentration exposure to methyl isocyanate. II. Blood chemistry and hematologic evaluations.

Human, rat, and guinea pig packed erythrocytes exposed to 100, 500, or 1000 ppm of methyl isocyanate (MIC) vapor in vitro showed a concentration-related inhibition of cholinesterase (ChE) activity. Rat and guinea pig packed erythrocytes showed an almost complete inhibition of ChE activity at 2000 ppm. In vitro exposures of human and guinea pig blood to 1000 or 2000 ppm of MIC vapor resulted in qualitative alterations in the electrophoretic mobility of hemoglobin (Hb) as measured by citrated agar electrophoresis. In rats and guinea pigs, neither IV injection of liquid MIC nor in vivo exposure to 1000 ppm of MIC by inhalation resulted in any inhibition of erythrocyte ChE activity or alteration in Hb electrophoretic mobility. As a result of these observations, it was concluded that neither ChE inhibition nor structural alteration of Hb were major contributing factors to death resulting from MIC exposure. Rats and guinea pigs receiving IV injections of liquid MIC showed an increase in creatine kinase (CK) levels. This increase could not be attributed to a specific isoenzyme of CK by ion exchange chromatography. Rats exposed to 100, 600, or 1000 ppm of MIC and guinea pigs exposed to 25, 125, or 225 ppm of MIC and bled immediately following a 15-min exposure or at 1, 2, 4, or 16 hr postexposure had the following alterations in blood parameters: an increase in CK, increases in hemoglobin concentration and hematocrit, reticulocytosis (rats only), neutrophilia, a decrease in blood pH and PO2, and an increase in blood PCO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological effects of short-term, high-concentration exposure to methyl isocyanate. III. Influence on gas exchange in the guinea pig lung.

The influence of methyl isocyanate (MIC) inhalation on the gas exchange function of the lungs in guinea pigs was studied by measuring arterial blood gases, pH, and tracheal pressure during constant-volume, artificial ventilation with air or 100% O2 at 40 and 120 min after exposure. A 15 min exposure to MIC at concentrations of 240 to 628 ppm caused a marked reduction in PaO2 and pHa and an elevated tracheal pressure during artificial ventilation. The low PaO2 was only slightly elevated when the animals were ventilated with 100% O2. Although the dry-wet lung weight ratio was reduced at the highest exposure concentration, the effect was not severe and no significant increase in lung water was found at the lower concentrations. MIC inhalation caused severe pulmonary blood shunting and ventilation/perfusion imbalance. This, in turn, led to hypoxemia, metabolic acidosis, and tissue hypoxia, which could produce death. The pulmonary gas exchange deficit likely resulted from bronchial and bronchiolar obstruction caused by sloughed epithelium and other debris from intra- and extrapulmonary airways.

Biological effects of short-term, high-concentration exposure to methyl isocyanate. IV. Influence on the oxygen-binding properties of guinea pig blood.

Whole blood oxygen equilibrium curves (O2 ECs), blood buffer lines, and several hematologic properties were determined for adult guinea pigs exposed to 700 ppm methyl isocyanate (MIC) for 15 min. MIC inhalation effected a significant reduction of blood O2 affinity; the half-saturation pressure (P50) at 38 degrees C increased from the control (untreated) level of 22.8 +/- 0.1 mm Hg to values ranging from 28.5 to 43.7 mm Hg for experimental animals. MIC exposure had no apparent influence on O2 EC shape or CO2 Bohr effect. Erythrocyte volume, [metHb], O2 binding capacity, and combined red cell organic phosphate concentration (DPG + ATP) were not affected by MIC treatment. However, experimental animals experienced a severe metabolic acid-base disturbance; blood lactate concentration ranged from 8.6 to 24.0 mmole/L. Results indicate that lactic acidosis was solely responsible for increased blood P50 of MIC-treated animals. No direct effects of MIC on hemoglobin function were observed. Reduced Hb-O2 affinity, in conjunction with severe hypoxemia, compromised the guinea pigs' capacity for pulmonary O2 loading; at PaO2 of 30 mm Hg, Hb-O2 saturation (S) decreased from 66% S for controls to 42% S for MIC-treated animals.

Biological effects of short-term, high-concentration exposure to methyl isocyanate. V. Morphologic evaluation of rat and guinea pig lungs.

The morphologic changes induced in the lungs of rats and guinea pigs exposed to high concentrations of MIC vapor (100, 600, and 1000 ppm in the rat and 25, 125, 225, and 675 ppm in the guinea pig) for a short time (15 min) in a static exposure chamber were evaluated at varying postexposure periods (0, 1, 2, 4, and 16 hr). The 675 ppm-exposed guinea pigs were evaluated only immediately following removal from the chamber. Attention was primarily focused on the intrapulmonary conducting airways and the parenchyma (gas exchange region) of the lungs. The severity of morphologic changes observed by light microscopy was directly correlated with exposure concentration and time postexposure in both species. Specifically, degenerative changes were observed in the bronchial, bronchiolar, and alveolar epithelium in both species. Quantitative differences were observed; 100 ppm of MIC in the rat resulted in much less damage than did 125 ppm of MIC in the guinea pig. Morphologic evidence of sloughing of large sheets of conducting airway epithelium with fibrin buildup and increased mucus production resulted in plugging of major airways and atelectasis. These observations support the hypothesis that tissue hypoxia was a major contributing factor resulting in death.

Acute, 9-day, and 13-week vapor inhalation studies on ethylene glycol monohexyl ether.

At ambient conditions, the low vapor pressure of ethylene glycol monohexyl ether (EGHE) allows for a maximum vapor concentration of approximately 85 ppm. In an acute inhalation study on Wistar albino rats, a 4-hr exposure to 83 ppm EGHE produced no clinical signs, body weight effects, mortality, or macroscopic lesions in thoracic or abdominal organs. Fischer 344 rats exposed for 9 days (6 hr/day) over an 11-day period, to 0 (control), 19, 41, or 84 ppm EGHE had decreased body weight gains and increased liver to body weight values at 84 ppm EGHE. No alterations of the hematology parameters or the morphology of the testes or liver were observed. In a subsequent study, rats were exposed to mean EGHE concentrations of 0 (control), 20, 41, or 71 ppm for 6 hr/day, 5 days/week, for 13 weeks. Urogenital wetness was observed in all EGHE-exposed groups of females and in males of the 71-ppm group. Decreased body weight gains were observed in both sexes of the 71-ppm group, and a slight decrease was also observed in females of the 41-ppm group. Increased absolute and/or relative liver weights were observed in both sexes of the 71-ppm group and to a lesser extent in the 41-ppm group. Possibly related to these findings in the liver were decreases in serum transaminases (aspartate and alanine aminotransferase) and sorbitol dehydrogenase, with an increase in alkaline phosphatase observed in the 71-ppm group of female rats. However, there were no gross or histopathologic lesions found to indicate impairment of the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

2,4-Pentanedione: 9-day and 14-week vapor inhalation studies in Fischer-344 rats.

Fischer-344 rats, in groups of 10 males and 10 females, were exposed for 9 days (6 hr/day) to 2,4-pentanedione (2,4-PD) vapor at mean concentrations of 805, 418, 197, and 0 (control) ppm. No deaths occurred, and the only adverse signs were of sensory irritation (partial closure of eyelids, periocular and perioral wetness) at 805 ppm. Also at 805 ppm were decreased body and organ weights, lymphocytosis, and moderate inflammation of the nasal mucosa. At 418 ppm there was a decrease in body weight gain and mild inflammation of the nasal mucosa. Apart from minimal nasal mucosal inflammation, there were no effects at 197 ppm. In the subchronic (14-week) study, rats were exposed (6 hr/day; 5 days/week) to 650, 307, 101, and 0 (control) ppm of 2,4-PD vapor, using groups containing 20 males and 20 females, with half being sacrificed at the end of the exposure period and the remainder kept for a 4-week postexposure recovery period. An additional 10 males were added to the 650 and 0 ppm groups for glutaraldehyde perfusion and subsequent electron microscopic examination of sciatic nerves. At 650 ppm, all females and 10 of 30 males died between the second and sixth weeks of exposure. These animals had acute degenerative changes in the deep cerebellar nuclei, vestibular nuclei and corpora striata, and acute lymphoid degeneration in the thymus. Seven of 15 male survivors of the 650 ppm group (combined 14-week and recovery sacrifices) had gliosis and malacia in the same brain regions, minimal squamous metaplasia in the nasal mucosa, decreased body and organ weights, lymphocytosis, and minor alterations in serum and urine chemistries. No ultrastructural evidence of peripheral neuropathy was observed. Except for central neuropathy, many of the adverse effects at 650 ppm were less marked in the 4-week recovery animals. No deaths occurred at 307 ppm, but females had slightly decreased body weight gains, and in both sexes there were minor alterations in hematology, serum chemistry, and urinalysis parameters, which were not present in the 4-week recovery animals. Rats exposed to 101 ppm showed no differences from the control rats. Subchronic exposure to 650 ppm of 2,4-PD vapor causes serious adverse biological effects. Under these study conditions, the minimum-effects concentration was 307 ppm, and the no-adverse effects concentration was 101 ppm.