Studies on coronary arteriopathy in dogs following administration of CI-1020, an endothelin A receptor antagonist.

A selective nonpeptide endothelin A (ETA) receptor antagonist, CI-1020, was administered to beagle dogs intravenously (i.v.) for 4 hours to 4 weeks. One animal/sex received CI-1020 at 1 mg/kg/hr intravenously for 4, 8, or 24 hours to investigate onset of arteriopathy. Control animals (1/sex) received the vehicle only. To determine reversibility of arteriopathy, 8 dogs/sex were given CI-1020 at 1 mg/kg/hr for 4 days. Two dogs/sex were sacrificed 1, 3, 8, and 29 days following cessation of infusion. Lesion development with prolonged exposure was investigated in 1 male dog. It was given CI-1020 by i.v. bolus at 120 mg/kg/day for 4 weeks and Monastral blue dye was administered i.v. to facilitate localization of vascular lesions. Coronary blood flow was determined in 4 dogs infused with CI-1020 at 0.3, 3, and 30 mg/kg for one hour at each dose. Macroscopically, hemorrhage or blue discoloration of Monastral blue was noted in the extramural coronary arteries along the coronary groove and atrium. Histologically, the earliest coronary changes were noted in animals sacrificed after 24 hours of treatment and characterized by medial hemorrhage and necrosis with a few infiltrating neutrophils. In the reversibility study, incidence and severity of arteriopathy was dependent on time of sacrifice following cessation of infusion. Acute necrotizing inflammation of arteries was present in all animals (n = 4) on day 1 postinfusion, whereas on day 8 postinfusion, lesions characterized by medial small pockets of trapped red cells, cell debris, and adventitial thickening were seen in 1 dog/sex. By day 29 postinfusion, coronary arteries were similar to controls. In the dog given daily i.v. bolus injections of CI-1020 for 4 weeks, arterial inflammatory lesions varied from acute to chronic, although most lesions were considered chronic active. Monastral blue pigments were noted in the wall of most arteries with chronic or chronic active lesions. Acute lesions were similar to those noted in day 1 postinfusion of the reversibility study. Medial smooth muscle necrosis and/or fibrosis with mixed inflammatory cell infiltrates characterized chronic or chronic active lesions. Smooth muscle proliferation and migration into the intima were also noted. There were no significant changes in coronary blood flow, coronary vascular resistance, or mean arterial blood pressure following CI-1020 infusion for 3 hours. In the 24-hour infusion study, plasma endothelin 1 (ET-1) levels were mildly elevated (1.5-4 fold) during CI-1020 infusion when compared to either pretest or control values. These results indicate that administration of endothelin antagonist (CI-1020) to dogs was associated with development of coronary arteriopathy, which was completely resolved within 29 days following cessation of treatment. With prolonged (4-week) CI-1020 treatment, arterial lesions at varying stages of development (acute, chronic active, chronic) were seen, suggesting that tolerance to treatment (up to 4 weeks) does not occur.     

Acute cardiovascular toxicity induced by an adenosine agonist-antihypertensive in beagles.

An adenosine agonist, designated chemically as (R)-N-(2,3-dihydro-1H-inden- 1-yl) adenosine, or CI-947, was administered to 3 male and 3 female beagles in oral doses of 5 mg/kg body weight. Multiple episodes of arrhythmia were recorded electrocardiographically with Holter monitors in 2 males and 2 females monitored up to 48 hr. One male and 1 female were necropsied at 24 hr and the remaining dogs were necropsied at 48 hr post-dosing. At 48 hr, multifocal perivascular epicardial and myocardial hemorrhage was noted grossly in 1 female. Microscopic coronary arterial alterations were present in all treated dogs irrespective of the occurrence of arrhythmias. At 24 hr, proteinic material and red cells were present in the media accompanied by minimal adventitial accumulation of neutrophils. At 48 hr, coronary arterial lesions progressed to media vacuolation, transmural necrosis, and perivascular accumulation of neutrophils. Ultrastructural alterations included: endothelial retraction, subendothelial accumulation of fibrin and platelets, necrosis of smooth muscle cells, and mural infiltration of granulocytes and monocytes. Coronary vascular injury may be due to altered hemodynamics associated with the coronary vasodilator properties of adenosine agonist compounds.     

CI-922--a novel, potent antiallergic compound--II. Activity in animal models of allergy

CI-922 (3,7-dimethoxy-4-phenyl-N-1H-tetrazol-5-yl-4H-furo [3,2-b]indole-2-carboxamide, L-arginine salt) is an effective antiallergic in guinea pig, rat, and canine models. This in vivo activity is attributed to its ability to inhibit inflammatory mediator release following antigen challenge in these species. Antigen-induced anaphylaxis in guinea pigs (collapse), which is mediated predominantly by histamine, was prevented by i.p. drug pretreatment. CI-922 (5 mg/kg, i.v.) reduced i.v. antigen-induced falls in pulmonary compliance in mepyramine-pretreated, anesthetized guinea pigs. By comparison, cromolyn sodium was inactive in both guinea pig models. In rats, CI-922 given immediately before antigen challenge (ID50 of 0.29 mg/kg, i.v.) was effective and twice as potent as cromolyn sodium and twenty times more potent than proxicromil in preventing i.v. antigen-induced pulmonary anaphylaxis. In addition, when the drugs were given 10 min before antigen challenge, only CI-922 caused a dose-related reduction of bronchoconstriction. CI-922 did not show direct antagonist activity when tested against a serotonin-induced bronchospasm, and exhibited only slight activity against a histamine-induced bronchospasm. CI-922 (0.3 mg/kg, i.v.) also reduced the bronchospasm caused by aerosol antigen (ascaris) challenge in spontaneously allergic dogs. In contrast, proxicromil was inactive in this dog model. The drug also inhibited passive cutaneous anaphylaxis in rats (ID50 of 0.2 to 0.3 mg/kg, i.v. and 0.7 to 6.4 mg/kg, p.o.). These data illustrate that CI-922 is active in several species in vivo, and has a spectrum of antiallergic activity significantly different from cromolyn-like drugs.     

Sequential morphological and biological changes in the glandular stomach induced by oral administration of catechol to male F344 rats.

Histogenesis and mechanisms of catechol-induced rat glandular stomach carcinogenesis were investigated in male F344 rats. Groups of 5 or 6 rats were treated with dietary catechol at doses of 1, 0.5, 0.1, and 0.01% for 12 hr or for 1, 2, 3, or 7 days or at a dose of 0.8% for 1, 2, 4, 12, and 24 wk; rats were then euthanatized. The initial morphological changes were edema of the gastric wall, inflammatory-cell infiltration, erosion in the pyloric region close to the duodenum, and considerable increase in apoptosis at 12 hr; later, changes included augmented DNA synthesis and cell proliferation, as evaluated by bromodeoxyuridine labeling index and thickness of mucosa, respectively, on day 1. Downward hyperplasia due to excess regeneration appeared at edges of ulceration at week 2. This lesion disappeared, and then submucosal hyperplasia appeared in the course of adenoma development. Only slight expression of c-myc or c-fos was apparent after 30-min oral administration or 1-, 3-, and 6-hr oral administration of catechol. No increase in lipid peroxide levels was evident in gastric epithelium fed catechol for 1 wk. The amount of catechol distributed in the glandular stomach and forestomach epithelium, which is not a target for carcinogenesis, did not differ 1, 3, 6, and 24 hr after a single intragastric dose of 75 mg/kg body weight. Amounts of catechol bound to tissue protein were also not specifically high in the glandular stomach. These results indicate that regenerative cell proliferation due to toxicity plays an important role in catechol-induced glandular stomach carcinogenesis. Protein binding and free radicals may not be largely responsible for the toxicity.     

Cutaneous lesions in the rat following administration of an irreversible inhibitor of erbB receptors, including the epidermal growth factor receptor

CI-1033 (canertinib) is an irreversible inhibitor of the erbB family of transmembrane tyrosine kinase receptors, including the epidermal growth factor (EGF) receptor. Various inhibitors of the EGF receptor, including CI-1033, have resulted in cutaneous toxicity in humans as a common adverse event. In a chronic toxicity study in rats, CI-1033 produced cutaneous lesions with morphologic characteristics similar to that reported in man. Here the authors describe in detail the dermal changes observed, along with other noteworthy findings of that study. Male and female Wistar rats (15/sex/group) were administered CI-1033 for 27 weeks at 2.5, 5, or 10 mg/kg (15, 30, or 60 mg/m(2), respectively) by gavage. Control animals (15/sex) received vehicle alone (aqueous 0.5% methylcellulose) in a dose volume of 5 mL/kg. Six animals/sex/dose were included for toxicokinetic evaluations. Skin lesions were the primary drug-related toxicity and occurred at > or = 2.5 mg/kg in a dose-dependent fashion. The major gross lesions were papules that evolved into crusts and scales that were first observed in weeks 1 and 3, respectively. Alopecia developed in conjunction with the papular eruptions. Skin changes were most pronounced in females, possibly due to higher drug levels. In week 13, CI-1033 plasma AUC(0-24) values were 527 to 1980 ng.h/mL in males and 844 to 2920 ng x h/mL in females at 2.5 to 10 mg/kg. Microscopic changes could be described as 3 patterns that affected the tail and body (haired skin). Pattern 1 consisted of epidermal changes that started as a superficial, perivascular spongiotic dermatitis with evolving epidermal hyperplasia, scale-crusts, and areas of ulceration. Areas of hyperplasia on the tail were often associated with the development of new hair follicles. Pattern 2 was characterized by a suppurative to pyogranulomatous infundibular folliculitis. Pattern 3 consisted of abnormally oriented hair follicles with malformed hair shafts that were associated with a deeper (isthmic) folliculitis; this correlated with alopecia. Elevations in bone marrow myeloid counts correlated with a peripheral leukocytosis, consistent with inflammatory changes in the dermis. In addition, hepatic cholestasis and epithelial atrophy in the gastrointestinal tract and vagina occurred at > or = 2.5 mg/kg. In conclusion, CI-1033 produced cutaneous lesions involving the epidermis and hair follicle, and the morphologic characteristics were similar to that reported in clinical studies with various inhibitors of the EGF receptor. These changes are consistent with pharmacologic inhibition of the EGF receptor in these tissues and demonstrate that the rat can serve as an animal model for investigating the mechanisms for this toxicity.     

Pharmacologic modulation of PAF-induced mortality in mice

The effect of antiinflammatory drugs, phosphodiesterase inhibitors, leukotriene and mediator antagonists and other drug classes were evaluated in a PAF-induced mortality model in mice. By the oral route of administration (–1 hr), dapsone (ED₅₀=25 mg/kg), BW 755C (ED₅₀=29 mg/kg), theophylline (ED₅₀=30 mg/kg) and LY-171,883 (ED₅₀=50 mg/kg) protected against PAF-induced lethality in the mouse. Other drugs that afforded protection when given at various dosing schedules and routes were NDGA (100 mg/kg, –18 hr p.o.), diphenyldisulfide (200 mg/kg, –18 hr p.o.), dexamethasone (1 mg/kg, –3 hr p.o.), dipyridamole (2 mg/kg, –2 min i.v.) and kadsurenone (10 mg/kg, –2 min i.v.). Nonsteroidal antiinflammatory drugs (NSAIDs) such as indomethacin were inactive and the combination of AA-861, a putative 5-LO inhibitor, and indomethacin also failed to prevent PAF-induced lethality. Therefore, our pharmacological data do not consistently support the notion that PAF-induced lethality is due unequivocally to leukotrienes derived from 5-lipoxygenase metabolism.     

Role of early vascular damage in the pathogenesis of gastric haemorrhagic mucosal lesions induced by indomethacin in rats

Early vascular injury is a key element in the pathogenesis of gastric haemorrhagic mucosal lesions which develop rapidly after intragastric (i.g.) administration of ethanol, HCl or NaOH. The sequence of vascular events leading to gastric lesions has not, however, been investigated in detail with ulcerogenic non-steroidal anti-inflammatory drugs such as indomethacin (IND). Accordingly, experiments were performed in rats using the vascular tracer Monastral blue to assess whether vascular lesions precede and are subsequently associated with mucosal lesions induced by oral (p.o.) or subcutaneous (s.c.) administration of IND. Fasted female Sprague–Dawley rats (150–180 g) were given IND either at 100 mg/kg, p.o. or 200 mg/kg s.c. and killed 15, 30, 120 or 240 minutes later. Monastral blue, 3% saline 1 ml/kg, was injected intravenously under ether anaesthesia 3 minutes before autopsy and the formalin fixed, glycerol cleared stomachs were examined microscopically for deposition of the dye particles on damaged blood vessels. The percentage area of Monastral blue labelled vessels (measured by stereomicroscopic planimetry) at 15 minutes after oral IND was 10.1 ± 1.5% (mean ± s.e.m.) of glandular stomach and increased progressively to 64.5 ± 3.0% at 240 minutes. Gastric haemorrhagic lesions (also measured by stereomicroscopic planimetry) were first evident at 30 minutes (0.2 ± 0.03%; mean ± s.e.m.), and developed progressively to 2.0±0.3% total area of glandular mucosa at 240 minutes. Subcutaneous injection of IND resulted in a delayed time of onset for the appearance and the extent of mucosal lesions (first appearing at 120 minutes, 0.1 ± 0.03% area) compared with that from oral administration of the drug, but as with oral IND the vascular damage (first appearance at 15 minutes, 7.5 ± 3.6%) clearly preceded the occurrence of gastric lesions. The observations of microvascular dye labelling were paralleled by observations of the electronmicroscopic appearance of endothelial cell disruption in the region adjacent to superficial mucous cells and accumulation of red blood cells in the interstitium at 20–60 minutes. We conclude that vascular injury precedes haemorrhagic mucosal damage in the pathogenesis of IND-induced acute gastric mucosal lesions.     

Effect of CI-949 and CI-959 on immune function and lymphoid organs in rats

The immunotoxic properties of two experimental antiallergic drugs, CI-949 and CI-959, were investigated. Wistar rats were gavaged once (CI-949) or twice (CI-959) daily for 21 days with the drugs. Immunotoxicity was assessed using the enzyme-linked immunoabsorbant assay (ELISA) for humoral immunity, a delayed-type hypersensitivity (DTH) procedure for cell-mediated immunity, and natural killer cell (NKC) activity to evaluate spontaneous cytotoxicity. Ratios of body weight to spleen, thymus, liver and kidney weights were determined. Routine histopathology was performed on lymphoid tissue and other body organs. Although 100 mg/kg/day of CI-949 had some stimulating effect on antibody production and NKC cytotoxicity, no consistent immunomodulation was apparent. Except for a significant increase in liver weight at the 100 mg/kg dose of CI-949, no other toxic effects were observed. In contrast to CI-949, CI-959 significantly (P less than 0.05) suppressed antibody production at the 100 mg/kg dose and impaired the DTH reaction, although not significantly. Natural killer cell cytotoxicity was unaffected by 100 mg/kg CI-959. Decreased body weight and histopathological lesions were observed in the thymus and spleen of rats administered 100 mg/kg CI-959. These lesions ranged from mild to severe lymphoid depletion which was also reflected in significantly (P less than 0.05) reduced spleen and thymus organ weight to body weight ratios. Since 100 mg/kg of CI-959 produced toxicological and pathological alterations in the exposed rats, these data suggest that CI-959 is not highly or specifically immunotoxic at dosages lower than those that alter conventional toxicological parameters used in new drug testing programs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antagonism by antipyretics of the hyperthermic effect of a prostaglandin precursor, sodium arachidonate, in the cat.

1. Injection of sodium arachidonate (100-400 mug) into lateral cerebral ventricles of unanaesthetized cats caused shivering and rapid development of dose-related hyperthermic responses. Unless arachidonate is hyperthermogenic per se, this indicates that in vivo formation of prostaglandins, or perhaps an endoperoxide intermediate, can cause hyperthermia. 2. Tolerance gradually developed when arachidonate was administered repeatedly at intervals of 1-7 days. Examination of the brains of several tolerant animals revealed in each case marked enlargement of the lateral ventricles which apparently accounted for the diminished response to arachidonate. 3. Sodium salicylate (40, 160 mg/kg, i.v.) antagonized arachidonate but only after a 3-4 hr latent period. 4. Paracetamol (10, 40 mg/kg, i.v.) reduced the hyperthermic effect of arachidonate but a dose of 40 mg/kg antagonized centrally administered bacterial endotoxin more effectively than it did arachidonate. 5. Indomethacin (40 mug/kg, i.v.) significantly reduced arachidonate-induced hyperthermia in only one of two studies. This reduction was comparable to the hypothermic effect of indomethacin in afebrile animals and was attributed to a non-specific action on thermoregulatory function rather than to inhibition of prostaglandin synthesis. Indomethacin antagonized endotoxin and leucocytic pyrogen to a greater degree than it did arachidonate. 6. Comparison of the relative effectiveness of the antipyretics in blocking hyperthermic responses to pyrogens and to sodium arachidonate indicates that, if prostaglandins do mediate pyrogen-induced fever, these antipyretics exert their primary at a step before prostaglandin synthesis.     

The effects of an anti-CD18 antibody (R15.7) in antigen-induced airway hyperresponsiveness (AH) and cell influx in guinea pigs

Aerosol ovalbumin challenge (OA) of sensitized guinea pigs induced airway hyperreactivity (AH) to i.v. acetylcholine (Ach) and serotonin (5-HT) 24 hr post OA. Bronchoalveolar lavage fluid 24 hrs after OA showed increased leukocytes compared to unsensitized unchallenged animals. Treatment with monoclonal antibody R15.7 (3 mg/kg i.v.,) 1 hr prior and 4 hours after OA prevented the induction of AH to Ach but not to 5-HT and reduced influx of leukocytes. We conclude: 1) antigen inhalation induces an increase in AH with an increase in proinflammatory cell influx and 2) treatment with anti-CD18 antibody inhibits cell influx and airway hyperreactivity.     

Catecholaminergic-serotonergic balance in the CNS and reproductive cycling in aging rats

Treatment with the serotonin (5-HT) reuptake inhibitor zimelidine, 20 mg/kg/24 hr, SC, for 14 days increased the duration of vaginal cycles in 3 month-old Long Evans hooded rats. It induced persistent vaginal estrus in 12 of 16 ten-month-old animals, and blocked reinitiation of vaginal cycles by L-dopa in 10 of 10 twenty-month-old rats. A single injection of zimelidine at 1400 hr did not alter the vaginal smear pattern of young or middle-aged cycling females or old constant estrus females. Also, a single dose of zimelidine at 1400 hr on the day of vaginal proestrus had no effect on serum LH values in young females. The serotonergic neurotoxin 5,7-dihydroxytryptamine, 4 micrograms, injected into the ventral and dorsal raphe areas (after desipramine, 25 mg/kg IP) reinitiated vaginal cycling in 8 of 13 twenty-month-old rats. These results suggest that age-dependent changes in serotonin metabolism may contribute to the age-dependent changes in luteinizing hormone secretion which eventually lead to the cessation of ovarian function in the rat and that alterations in serotonin function are an important component of the mechanism by which treatments with catecholamine precursors reinstate ovarian function in the old female rat.     

Effect of SA-103 on experimental allergic models in vivo and in vitro--comparison with disodium cromoglycate.

The anti-allergic action of N-[4-(4-methoxyphenyl)-2-thiazolyl]-1H-tetrazol-5-carboxamide (SA-103) was investigated and compared with that of disodium cromoglycate (DSCG). 1) Oral administration of SA-103 (0.1-10 mg/kg, p.o.) showed dose-dependent inhibition of 48 hr homologous passive cutaneous anaphylaxis (PCA) in rats. The inhibition rate (50%) of the compound at 1 mg/kg was comparable to that of DSCG at 1 mg/kg (i.v.). 2) Both of the drugs concentration-dependently inhibited the release of in vitro anaphylactic histamine from rat peritoneal exudate cells, but SA-103 was 1,000 times as potent as DSCG. 3) High doses (50 and 100 mg/kg, p.o.) of SA-103 tended to suppress 7-day homologous PCA in guinea pigs by only 20-30%. DSCG (100 mg/kg, i.v.) did not influence the reaction. 4) Neither anaphylactic histamine nor leukotriene release from guinea pig lung fragments was markedly influenced by SA-103 (10(-8)-10(-5) g/ml) or DSCG (10(-5)-10(-3) g/ml). 5) The histamine and serotonin induced contractions of the isolated guinea pig ileum were minimally enhanced or suppressed by very high concentrations (10(-4) g/ml) of SA-103 and DSCG. In addition to the above results, prolonged treatment with either compound before antigen challenge decreased the inhibitory response to anaphylactic histamine release from rat peritoneal cells. It is suggested, therefore, that the main mechanism(s) of the anti-allergic action of SA-103 is similar to that of DSCG, and SA-103 may be expected to be effective against allergic diseases.     

Daily,limited access to methamphetamine self-administration during pregnancy leads to increased methamphetamine sensitivity in adult offspring

Methamphetamine use by women, even throughout pregnancy, is common. But there is limited knowledge about the effects in prenatally methamphetamine-exposed children. This study investigated how prenatal methamphetamine exposure in rats, via maternal i.v. self-administration, affected the sensitivity of adult offspring to methamphetamine in comparison with controls. The offspring were generated from dams either self-administering methamphetamine daily under limited-access conditions prior to and throughout pregnancy, or their respective saline-yoked control dams. Spontaneous and methamphetamine-induced locomotor activity was assessed in male and female offspring of both exposure groups after a range of methamphetamine doses. In a separate group of offspring, acquisition of i.v. methamphetamine self-administration, responding under fixed and progressive ratio schedules of methamphetamine reinforcement, and reinstatement of extinguished drug-seeking behavior were assessed. Methamphetamine dose-dependently increased locomotor activity in both exposure groups. However, methamphetamine-exposed males showed significantly enhanced locomotor activity compared with controls at 1 mg/kg, and methamphetamine-exposed females showed significantly enhanced locomotor activity compared with controls at 3.2 mg/kg. Methamphetamine-exposed offspring of both sexes acquired methamphetamine self-administration faster and showed overall higher levels of methamphetamine-induced reinstatement compared with controls. Taken together, these results indicate that prenatal methamphetamine exposure to relatively low levels alters methamphetamine sensitivity in male and female adult offspring.     

The opiatergic link between the antiarrhythmic effect of adaptation and hypoxia in the model of ischemia and reperfusion in vivo

Rat adaptation to repeated periods of hypobaric hypoxia has been found to prevent the occurrence of ischemic and reperfusion ventricular arrhythmias on a 10-minte coronary artery occlusion model. Inhibition of delta-opioid receptors by intravenous administration of the selective delta-opioid antagonist TIPP (psi) in a dose of 0.5 mg/kg, intravenously (i.v.), completely abolished the antiarrhythmic effect of adaptation to hypoxia. Inhibition of mu-opioid receptors by CTAP (0.5 mg/kg, i.v.) or kappa-receptors by nor-binaltorphimine (9 mg/kg i.v.) had no effect on the incidence cardiac rhythm disturbances in adapted rats during coronary artery occlusion and reperfusion. Therefore, these findings suggest that delta-opioid receptors play an important role in inhibiting arrhythmia formation in this model.     

Naloxone does not influence a pyrogen fever in rabbits

Rabbits were made febrile by an intravenous injection of homologous endogenous pyrogen (Interleukin 1). When naloxone (0.1 mg/kg i.v.) followed by 0.06 mg (kg·hr)^–1 infusion) was given at the same time as the pyrogen, the resulting fever was indistinguishable from that following pyrogen alone. It appears unlikely that opioid receptors which are blocked by naloxone play any important part in the fever process.     

CGS 22745: A selective orally active inhibitor of 5-lipoxygenase

CGS 22745, and aralkyl hydroxamic acid, inhibited 5-hydroxyeicosatetraenoic acid (5-HETE) and leukotriene B₄ (LTB₄) synthesis in guinea pig leukocytes (IC₅₀=0.6M). The compound did not appreciably affect cyclooxygenase (ram seminal vesicles), 12-lipoxygenase and thromboxane synthase (human platelets) or 15-lipoxygenase (human neutrophils). CGS 22745 inhibited A23187-induced formation of LTB₄ in blood (IC₅₀'s of 4.3, 0.56 and 3.2 M for human, dog and rat, respectively). At 1 mg/kg i.v. in dogs, it caused 96% inhibition of A23187-stimulated LTB₄ formationex vivo after 5 min. Its effective biological half-life was >160 min. In dogs at 3 and 10 mg/kg p.o., CGS 22745 inhibitedex vivo A23187-stimulated LTB₄ formation at 3 hr by 48% and 97%, respectively. The inhibition persisted up to 6 hr (26% at 3 mg/kg; 49% at 10 mg/kg). CGS 22745 (3, 10 and 30 mg/kg p.o.) inhibited exudate formation, mononuclear cells and PMN accumulation in a dose-dependent manner during the late phase (48 and 72 hr) of carrageenan-induced pleurisy in the rat.     

Involvement of substance P as a mediator in capsaicin-induced mouse ear oedema

We examined the involvement of substance P (SP) in mouse ear oedema induced by topical application of capsaicin (250 µg/ear). Reapplication of capsaicin at 4h, 24h, and 48h after initial treatment did not induce a second oedema response. Oedema induced after the second application was significantly (p<0.01 orp<0.001) suppressed for up to 30 days but was observed when capsaicin was applied 40 days after initial treatment. Topical pretreatment of ears with capsaicin at 4h, 24h and 48h before i.v. injection of SP (5 µg/kg) did not cause a significant inhibition of plasma extravasation in ear skin. NK₁ receptor antagonists such as RP 67580 (ED₅₀:0.19 mg/kg, i.v.), spantide II (ED₅₀:0.33 mg/kg, i.v.), and GR 82334 (ED₅₀:0.26 mg/kg, i.v.), inhibited capsaicin-induced ear oedema, whereas SR 48968 (2.0 mg/kg, i.v.), a NK₂ receptor antagonist, had no effect. Furthermore, RP 67580 (0.5 kg/mg, i.v.) inhibited the oedema response induced by reapplication of capsaicin at 50 days after initial treatment. These results indicate that tachyphylaxis of capsaicin-induced oedema is reversible and suggest that this response may be due mainly to a reduction of SP in sensory neurones but not to any loss of responsiveness of NK₁ receptors. We also conclude that SP and NK₁ receptors are involved predominantly in the development of capsaicin-induced mouse ear oedema.     

Evaluation of safety and pharmacokinetics of administering intravenous busulfan in a twice-daily or daily schedule to patients with advanced hematologic malignant disease undergoing stem cell transplantation.

Intravenous busulfan (i.v. BU) has demonstrated safety when administered at 0.8 mg/kg per dose i.v. every 6 hours x 16 doses. We evaluated the safety and pharmacokinetics (PK) of giving the same total daily i.v. BU dose (3.2 mg/kg) either divided as a twice-daily infusion or as a single infusion to patients undergoing hematopoietic stem cell transplantation (HSCT). Twelve patients with hematologic malignant disease were treated; 7 patients had non-Hodgkin's lymphoma, 4 patients had acute myeloid leukemia, and 1 patient had chronic myelogenous leukemia. The first cohort (group A) received, on the basis of actual body weight, i.v. BU at 1.6 mg/kg per dose over 4 hours every 12 hours for 4 days (day -7 to day -4). The second cohort (group B) received 3.2 mg/kg per dose of i.v. BU (same total dose as group A) as a single infusion over 4 hours daily for 4 days. In both groups the i.v. BU was followed by cyclophosphamide 60 mg/kg daily for 2 days (day -3 and day -2). Blood specimens were collected on the first, fifth, and seventh doses for group A and on the first and fourth doses for group B to determine the disposition of i.v. BU. Peripheral blood stem cells (autologous in 7 cases and HLA-matched allogeneic in 5 cases) were given 2 days after completion of cyclophosphamide administration (day 0), and granulocyte colony-stimulating factor 5 microg/kg was started on the same day. GVHD prophylaxis consisted of tacrolimus plus methotrexate for recipients of allogeneic stem cells. One patient developed presumed fungal pneumonia and died of multisystem organ dysfunction on day +21 before hematologic reconstitution could be evaluated. Another was reported to have sudden death of undetermined cause at home on day 40. The remaining patients had engraftment (absolute neutrophil count >500/microL) at a median of 11 days and sustained platelet counts >20,000/microL at a median of 14 days. Significant regimen-related toxicity (grade III-IV) was limited to hepatic toxicity (2 cases) catheter infection (2 cases), epistaxis (3 cases), diarrhea (1 case), anorexia (1 case), mucositis (1 case), hyperglycemia (1 case), pneumonia (1 case), and sepsis (1). In group B there was 1 case of mild venoocclusive disease, which resolved without sequelae. No central nervous system or pulmonary toxicity was noted. Pharmacokinetic parameters, including clearance, half-life, maximum concentration, and area under the curve, demonstrated that the first dose profile was highly predictive of later dose PK profiles. No accumulation of the drug was noted. The change in dosing schedule did not increase toxicity or end-organ damage despite higher plasma concentration-times. Although further study for long-term efficacy is warranted, i.v. BU can be given safely with reproducible results on a twice-daily divided or single-daily dosing schedule to patients undergoing HSCT.     

Cardiac damage in rodents after exposure to bis(2-chloroethoxy)methane

We report that an environmental agent, bis(2-chloroethoxy)methane (CEM), caused cardiac toxicity in male and female F344 rats and B6C3F1 mice exposed to the chemical by dermal administration at doses of 0, 50, 100, 200, 400 or 600 mg/kg 5 days a week for up to 14 weeks. Treatment-related deaths occurred in 10/10 male and 10/10 female rats at 600 mg/kg, in 2/10 female rats at 400 mg/kg, and in 3/10 female mice at 600 mg/kg. The heart lesions were more severe in rats than mice, and more severe in females than males. In rats, the no-observed-adverse-effect level (NOAEL) for the heart lesions was 200 mg/kg for males and 100 mg/kg for females; in mice, it was more than 600 mg/kg for males and 200 mg/kg for females. Multifocal, widespread vacuolization of the myocytes comprised the main morphological feature of the lesions, and only in rats was it accompanied by mononuclear cell infiltration, myocytic necrosis and atrial thrombosis. Hearts from male rats were immunohistochemically stained for troponin T (cTnT) protein. Loss of cytoplasmic cTnT correlated with histopathological damage only in the 600 mg/kg animals. CEM is metabolized to thiodiglycolic acid, a chemical that causes mitochondrial dysfunction. It is hypothesized that mitochondrial damage leads to the heart toxicity from bis(2-chloroethoxy)methane.     

Sex differences in renal damage induced in the mouse by Amanita virosa

The sensitivity of male and female mice to Amanita virosa was compared. Dried, homogenized mushroom was given orally by stomach tubing at doses of 100, 200, 400 and 800 mg dried mushroom/kg body weight. Both in males and in females, the kidneys were the only organs showing macroscopical changes. The dose of 100 mg/kg caused renal damage in females, whereas in males the first signs of kidney damage were seen at the dose of 400 mg/kg. The renal lesions observed in the males were located in the cortex, while in the females they were limited to the outer stripe of the outer medullary zone. Testectomy diminished the nephrotoxicity of A. virosa in male mice and caused changes in the localization of renal lesions.