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ABSTRACT: Tetra-iso-propyl 2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethyl-1,1-diphosphonate (CAS 126411-13-0, SR-9223i) is a member of a new class of compounds with multiple antiatherosclerotic activities. This report not only describes the cholesterol-lowering properties in four species of animals fed normocholesterolaemic diets but also reductions in lipid deposition in the arteries of cholesterol-fed New Zealand white rabbits following the administration of SR-9223i. Plasma cholesterol concentrations were reduced in mice by 27% (200 mg/kg/day administered in the diet for 10 days), in hamsters by 33% (200 mg/kg/day administered in the diet for 8 days), in dogs by 16% (25 mg/kg/day p.o. for 28 days) and 23% (75 mg/kg/day p.o. for 28 days) and in monkeys by 22% (25 mg/kg/day p.o. for 28 days). Further, the deposition of cholesterol, especially in the esterified form, in the aortae of cholesterol-fed New Zealand white rabbits was inhibited by SR-9223i (50 and 100 mg/kg/day p.o.). At the higher dose, the cholesteryl ester content of the aorta was half that of control animals. SR-9223i, at both doses, also inhibited the accumulation of cholesterol in the liver. SR-9223i has been shown to suppress HMG CoA reductase activity, inhibit ACAT activity and prevent lipid oxidation. These activities, demonstrated in vitro, have now been shown to translate into lipid lowering and antiatherosclerotic activities in vivo.
Arzneimittel-Forschung 05/2000; 50(4):380-6. · 0.72 Impact Factor
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ABSTRACT: SR-12813 inhibits cholesterol biosynthesis in Hep G2 cells via an enhanced degradation of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. Here we also show that SR-12813 inhibits cholesterol biosynthesis in vivo. A sterol balance study was performed in normolipemic beagle dogs. The dogs were given SR-12813 orally at dosages of 10 and 25 mg/kg/day for a period of 9 days. After 7 days plasma cholesterol was decreased by 15% in the 10 mg/kg/day group and by 19% in the 25 mg/kg/day group. Using a dual isotope technique no effects on intestinal cholesterol absorption were observed. The sterol balance indicated that endogenous synthesis of cholesterol was reduced by 23% in the 10 mg/kg/day group and by 37% in the 25 mg/kg/day group. Plasma lathosterol-cholesterol levels in dogs treated with 25 mg/kg/day SR-12813 were reduced by 56%, confirming a reduction of the cholesterol biosynthesis. Treatment with SR-12813 or the HMG-CoA reductase inhibitor lovastatin resulted in a large decrease in low density lipoprotein (LDL) cholesterol. It is concluded that SR-12813 reduces cholesterol biosynthesis in the dog model which results in a decrease of bile acid excretion, cholesterol excretion and plasma cholesterol level. The in vivo profile of SR-12813 is very similar to that of direct HMG-CoA reductase inhibitors, although the mode of action of the compound is unique.
Atherosclerosis 10/1997; 133(2):203-12. · 3.79 Impact Factor
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ABSTRACT: We introduce here a new fluorescence microscopy technique for en face analysis of the atherosclerotic fatty streaks (FS). This technique is semiquantitative and has the sensitivity and resolution to map lipids to individual cells in FS less than 100 microns in diameter. New Zealand White rabbits were fed an atherogenic diet for up to 26 weeks. Aortas were fixed in formalin and stained en bloc with the fluorescent dyes Nile red and filipin. Fluorescent staining was validated by correlating microfluorimetric and biochemical measurements of the lipid content in FS. To determine the cell types associated with the different staining patterns, FS were also evaluated by transmission electron microscopy (TEM) and immunohistochemistry (IH). Correlation of microfluorimetry, TEM, IH, and biochemical data indicated that regions rich in non-esterified cholesterol stained with filipin and fluoresced blue owing to accumulations of lipid vesicles and/or cholesterol crystals. Regions rich in neutral and polar lipids stained with Nile red and fluoresced yellow or orange, respectively, owing to accumulations of lipids in both macrophages and smooth muscle cells (SMC). Digital overlays of the filipin and Nile red images revealed that larger lesions (> 0.5 mm diameter) had a "nested" distribution of lipids, with a blue (filipin) fringe surrounding an orange (Nile red) fringe surrounding a yellow (Nile red) center.
Journal of Histochemistry and Cytochemistry 05/1997; 45(5):743-53. · 2.72 Impact Factor
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ABSTRACT: Alterations of the cardiac membranous ventricular septum were studied using macrodissection, scanning electron and light microscopy of fetal, weanling, and adult Sprague-Dawley rats. Membranous ventricular septal defects (VSDs) were observed in 2.0% of fetuses on day 21 postcoitus (pc) but not in weanling or adult rats. The most common observation was a nonpatent depression in the membranous septum with an incidence of 38.1, 10.5, 4.3% for fetuses on days 17, 19, or 21 pc, respectively, 11.8% for weanlings, and 9.1% for adults. VSDs were characterized by a split in the endocardial cushion cells in the interventricular component of the membranous septum. Nonpatent depressions were characterized by a split in the endocardial cushion cells in the atrioventricular component of the septum, and they persisted postnatally as a blind-ended diverticulum directed above the tricuspid valve. The cardiovascular teratogens, trimethadione and trypan blue, produced in fetuses nonpatent depressions and VSDs morphologically similar to untreated fetuses. Maternal diet restriction (25% of controls) lowered fetal (day 21 pc) body weight by 47% but did not affect the incidence of ventricular septal alterations, suggesting that intrauterine growth retardation is not necessarily associated with alterations in the development of the ventricular septum. We conclude that neither VSDs nor nonpatent depressions in Sprague-Dawley rats affect postnatal survival and that VSDs close spontaneously during neonatal life.
Teratology 04/1997; 55(3):185-94.
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ABSTRACT: Macrophage-derived foam cells are a prominent component of developing atherosclerotic lesions. We describe an in vitro model of foam cell formation which mimics some aspects of the evolution of foam cells in mature atherosclerotic lesions. Thioglycollate-elicited mouse peritoneal macrophages were incubated with copper-oxidized LDL (ox-LDL) for periods up to 168 hr. Identifiable foam cells were present after incubation with ox-LDL at 24, 72, and 168 hr. Control cells incubated without ox-LDL did not form foam cells. Fluorescence microscopy after staining with Nile red exhibited progressive accumulation of lipids, and transmission electron microscopy (TEM) showed distinct ultrastructural changes over time. Macrophages at 24 hr had a few non-membrane-bound lipid droplets but were otherwise identical to control cells. These lipid droplets fluoresced yellow-gold after Nile red staining. After 72 hr of incubation with ox-LDL, in addition to increased numbers of non-membrane-bound lipid inclusions, macrophages contained membrane-bound multilamellar lipoid structures. These multilamellar structures corresponded to areas of reddish-orange fluorescence after Nile red staining. In macrophages incubated with ox-LDL for 168 hr, the amount of cellular lipid was further increased and cholesterol crystal profiles were apparent within some multilamellar lipoid structures. Biochemical analysis showed that the total cholesterol content steadily increased over 168 hr. The increase in total cholesterol was accompanied by a dramatic increase in free cholesterol between 72 and 168 hr. These results demonstrate that long-term incubation of macrophages with ox-LDL increased lipid deposition in cultured cells and that, under the conditions studied, cholesterol crystals formed in macrophage foam cells. Moreover, this system allows investigation of the evolution of foam cells showing some characteristics of those found in atherosclerotic lesions.
Journal of Histochemistry and Cytochemistry 11/1995; 43(10):1071-8. · 2.72 Impact Factor
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ABSTRACT: The cross-sectional structure of the vasculature is comparatively simple, comprising three layers--the intima, adjacent to the lumen, the media, and the adventitia. Notwithstanding this simplicity, the vessels are host to a variety of reactions to injury. Two cell types, endothelial cells of the intima and smooth muscle cells of the media, are principal targets of damage and repair. The endothelial cells of the intimal layer of the vessel wall present a macromolecular barrier and are important in maintaining vessel integrity. When the integrity is compromised by physical or chemical injury, endothelial cells play a key role in the repair processes. The use of single-cell wound models allows the mechanisms of damage and subsequent repair to be studied in depth. Repair processes can be observed using time-lapse photography and differences between cytoskeleton changes during repair and reendothelialization of small and large wounds can be discriminated. In rats treated with the plant toxin monocrotaline, pulmonary vascular injury occurs which manifests as thrombosis and remodeling with consequent progressive pulmonary hypertension. In vivo and in vitro studies of the mechanism of monocrotaline toxicity suggest that the endothelial cells are an important target. In vitro studies show monocrotaline to be directly cytotoxic; in cells that survive, there are functional changes to the endothelial cells, resulting in a decreased repair capability which may lead to the complex, progressive lung lesions that develop. The other target cells of the vasculature are the smooth muscle cells of the media. Ingestion of primary amines allylamine and beta-aminopropionitrile (beta-APN) results in chronic vasculotoxicity to the aorta and medium-sized arteries. For allylamine, subtle changes in smooth muscle result in medial hypertrophy and subintimal proliferation. The changes are slow to occur, taking weeks or months of repeated treatment. For beta-APN, which is the active ingredient of the toxic sweet pea Lathyrus odoratous, vascular toxicity is manifested by fatal rupture of aortic aneurysms. When these agents are administered concomitantly, a synergistic acute smooth muscle necrosis occurs in large elastic arteries and degenerative changes are seen in muscular arteries. A change in the target for toxicity of allylamine toward the vasculature may be responsible for this synergistic toxic insult. Medial smooth muscle necrosis is also noteworthy after administration of certain pharmaceutical agents of diverse structure and pharmacological activity. These agents induce arteriopathies in dogs and rats, although at different sites. In dogs, the coronary arteries are susceptible, whereas in rats the mesenteric arteries are the principal sites of injury.(ABSTRACT TRUNCATED AT 400 WORDS)
Toxicology and Applied Pharmacology 07/1995; 132(2):177-95. · 4.45 Impact Factor
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ABSTRACT: Azaspiranes are novel immunomodulators which are effective in a variety of autoimmune diseases. One azaspirane analog, SK&F 105685 (N,N-dimethyl-8,8-dipropyl-2-azaspiro [4.5] decane-2-propanamine dihydrochloride), caused a decrease in total serum cholesterol in dogs after oral administration. To determine whether an effect on cholesterol was common to this class of compounds, the immunomodulatory activity was compared with the cholesterol-lowering activity of six azaspirane analogs. The compounds were given to beagles at a dose of 1 mg/kg p.o. for 28 days, and the effect on serum cholesterol was determined. The results from this study showed a clear dissociation between the immunomodulatory and hypocholesterolemic activities of these compounds. Studies performed to determine the mechanism of the decrease in serum cholesterol caused by SK&F 105685 indicated that it was not due to inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase or acyl-CoA:cholesterol acyltransferase activities, or to a potentiation of cholesterol-7 alpha-hydroxylase activity. In addition, analysis by gas chromatography of the nonsaponifiable sterol fraction in dog plasma after treatment with SK&F 105685 or SK&F 106333 showed a decrease in cholesterol and an accumulation of lathosterol and an unknown sterol, indicating that the conversion of these sterols is inhibited and cholesterol synthesis is blocked at these steps. SK&F 105685 affected the sterol profile in human hepatoblastoma cells (Hep G2) in a similar way. Characterization of the unknown sterol by gas chromatography and mass spectrometry indicated that the unknown sterol is very similar to cholesterol and lathosterol, but its identity has yet to be established. These results show that the hypocholesterolemic effects of azaspiranes are related to inhibition of one or more of the final steps in the biosynthetic pathway of cholesterol.
Journal of Pharmacology and Experimental Therapeutics 03/1995; 272(2):689-98. · 3.83 Impact Factor
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ABSTRACT: Fenoldopam mesylate (FM), a selective, postjunctional, dopaminergic (DA1) vasodilator, causes a novel lesion of large caliber splanchnic arteries (100 to 800 microns) in the rat characterized by necrosis of medial smooth muscle cells and hemorrhage. FM does not induce lesions in other vascular beds of the rat or in dogs or monkeys. Dopamine, like FM, causes hemorrhagic lesions of large caliber splanchnic arteries in the rat, as well as fibrinoid necrosis of small caliber arteries (less than 100 microns) of the splanchnic, cerebral, coronary, and renal vascular beds. Dopamine, an alpha- and beta-adrenoceptor and dopaminergic agonist, is used clinically, principally as a pressor agent. Because these arterial lesions were believed to result from the pharmacologic activity of these two compounds, the role of vascular receptor subtypes in their pathogenesis was investigated. Rats were coexposed to either FM or dopamine and a variety of receptor antagonists (alpha, beta, DA1, DA2, and 5HT2). In rats coexposed to the alpha-adrenoreceptor antagonist phenoxybenzamine (PBZ) and either FM or dopamine, the incidence and severity of hemorrhagic lesions of large caliber arteries were increased; PBZ, however, prevented the formation of dopamine-induced fibrinoid lesions in arteries of small caliber. SK&F 83566-C, a selective DA1 dopaminergic receptor antagonist, prevented the induction of FM and dopamine-induced hemorrhagic lesions of large caliber arteries. Rats exposed concurrently to dopamine, phenoxybenzamine, and SK&F 83566-C were free of all arterial lesions. The other receptor antagonists tested did not prevent arterial injury. Thus, the induction of splanchnic arterial lesions in the rat by dopamine and FM is caused by stimulation of, and interaction between, alpha-adrenoceptors and dopaminergic DA1 receptors. Activation of the postjunctional, dopaminergic (DA1) receptor is causally associated with the induction of novel hemorrhagic lesions of large caliber splanchnic arteries in the rat.
American Journal Of Pathology 09/1989; 135(2):339-49. · 4.89 Impact Factor
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ABSTRACT: In each of 8 rabbits, a fiberoptic with a 1.5 mm diameter metal tip was inserted into the abdominal aorta. After preheating with 8-10 watts of argon laser energy, the metal tip was passed through the external iliac artery. Thermal injury was evaluated by histology and by measuring arterial contractions and wall mechanics. The contralateral iliac artery was used as a control. Laser thermal angioplasty (LTA) produced foci of coagulation necrosis, medial thinning, and wall rupture. Concomitantly, maximal arterial contractile force was reduced by 80% (p less than 0.01) and arterial wall stiffness was decreased (p less than 0.05). These changes may have clinical implications with regard to the incidence and severity of vasospasm and restenosis following angioplasty.
CardioVascular and Interventional Radiology 04/1989; 12(2):83-7. · 2.09 Impact Factor
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ABSTRACT: Fenoldopam mesylate (FM), a selective post-junctional dopaminergic (DA1) vasodilator, causes lesions of large caliber splanchnic arteries (100-800 microns) in the rat characterized by necrosis of medial smooth muscle cells and hemorrhage. FM does not induce lesions in other vascular beds of the rat, or in dogs or monkeys. Dopamine, like FM, causes hemorrhagic lesions of large caliber splanchnic arteries in the rat, as well as fibrinoid necrosis of small caliber arteries (less than 100 microns) of the splanchnic, cerebral, coronary and renal vascular beds. Dopamine is an alpha- and beta-adrenoceptor and a dopaminergic receptor agonist. Because these arterial lesions are thought to result from the pharmacologic activity of these 2 compounds, we sought to ascertain the presence of DA1 receptors in mesenteric arteries of the rat and to determine the role of these or other vascular receptor subtypes in lesion induction. We also studied the process of repair after arterial injury caused by FM or dopamine. The presence of DA1 receptors was confirmed in isolated perfused mesenteric arteries by standard pharmacologic techniques; stimulation by FM resulted in vasodilation which was inhibited by the DA1 receptor antagonist SK&F 83566-C. Likewise, SK&F 83566-C prevented the induction of hemorrhagic lesions of large caliber arteries in rats upon infusion of FM or dopamine. In rats co-exposed to the alpha-adrenoreceptor antagonist phenoxybenzamine (PBZ) and either FM or dopamine, the incidence and severity of hemorrhagic lesions of large caliber arteries were increased, but PBZ prevented the formation of dopamine-induced fibrinoid lesions in arteries of small caliber. Rats exposed concurrently to dopamine, phenoxybenzamine, and SK&F 83566-C were free of all arterial lesions. Thus, the induction of splanchnic arterial lesions in the rat by dopamine and FM is caused by stimulation of, and interaction between, alpha-adrenoceptors and dopaminergic DA1 receptors. Fibrinoid lesions of small arteries (alpha-adrenoceptor-mediated) were repaired, as observed morphologically by 14 d after exposure to dopamine. Hemorrhagic lesions of large caliber arteries (DA1 receptor-mediated) had undergone significant repair by 28 d after exposure to FM but these arteries possessed a thicker media surrounded by adventitial fibrosis. Thus, morphologically distinct receptor-mediated splanchnic arterial lesions induced by dopaminergic and alpha-adrenoceptor agonists follow a markedly different course of repair. Arterial lesions induced by FM or dopamine by activation of post-junctional dopaminergic DA1 receptors may represent a model of polyarteritis nodosa.
Toxicologic Pathology 02/1989; 17(1 Pt 2):203-13. · 1.91 Impact Factor
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ABSTRACT: The immunotoxicologic effects of drugs on host defense have been studied widely using various animal models of infection. Here we describe a new approach to testing host defense by using a single organism (Candida albicans) in CBA/J mice. The model is configured to test 3 effector systems via different routes of inoculation to stimulate different effector arms of the immune response. Nonspecific immunity was evaluated by C. albicans colony-forming unit (CFU) count from the spleen at 2 hr (uptake) and > or = 22 hr (clearance) following intravenous inoculation. Cell-mediated immunity was assessed by CFU count from an intramuscular injection site 6 days postinoculation. Humoral immunity was assessed by anti-Candida antibody titer, following multiple subcutaneous immunizations with C. albicans. Finally, overall immunity was evaluated following intravenous injection using survival as the endpoint. Histopathological, immunohistochemical, and electron microscopic evaluation of selected tissues revealed the involvement of the expected cell types in the different effector systems. Several immunomodulatory drugs--dexamethasone, cyclosporine, liposomal muramyltripeptide phosphatidylethanolamine, and SK&F 105685--were evaluated in the C. albicans model. Dexamethasone impaired host defense against C. albicans by suppressing all endpoints measured. Similarly, cyclosporine showed broad immunosuppressive activity, with the exception of yeast uptake from the spleen. In contrast, muramyl tripeptide-phosphatidylethanolamine enhanced all but cell-mediated immunity to C. albicans. SK&F 105685 displayed both stimulatory and inhibitory effects on immune responses to the infection. Our studies demonstrate that a single organism-based approach can be a useful method for evaluating the immunological hazards of drugs on host resistance to infection.
Toxicologic Pathology 25(4):351-62. · 1.91 Impact Factor
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ABSTRACT: Appropriate dosage selection is a key element in the design of toxicology studies and, hence, is the first step in the process of evaluating the safety of a new chemical or pharmaceutical agent. This demands careful consideration of exposure to the drug or chemical under investigation in relation to the pharmacological or toxicological effects it evokes in an experimental animal. Toxicokinetic data provide this perspective, but they should not be considered exclusively of other data which reflect the specific activity, potency, or metabolism of the drug or chemical in each individual test species. It is equally inappropriate to base dosage selection in toxicology studies exclusively on functional or morphological endpoints that cause effects outside the range which can be accommodated by homeostatic mechanisms and repair processes. Finally, extrapolation of toxicokinetic data across species lines can lead to serious miscalculations with respect to both dosage selection and the process of risk assessment. In each case, decisions should be based on the integration of toxicokinetic data with other measures and endpoints of biological and toxicological effect.
Toxicologic Pathology 22(2):112-23. · 1.91 Impact Factor
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ABSTRACT: Drugs that inhibit the low-Km, cGMP-inhibitable form of phosphodiesterase III (PDE III) are associated with arterial lesions in the extramural coronary arteries of dogs following oral and intravenous administration at high doses. Acute coronary arterial lesions have been investigated following administration to the dog of SK&F 95654, a potent PDE III inhibitor, and the progression of the lesion defined. Groups of 3 male beagle dogs received a single 2-hr infusion of SK&F 95654 at 8 mg/kg/hr and the characteristics of the coronary arterial lesions were evaluated at 1, 3, 10, and 34 days postdosing by light, scanning, and transmission electron microscopy. At 24 hr postdosing, the arterial lesion was characterized by segmental or circumferential necrosis of medial smooth muscle cells and hemorrhage; adventitial hemorrhage was also noted, particularly in the right atrial artery. Ultrastructural evaluation showed extensive medial necrosis, characterized by loss of smooth muscle cells and their replacement by cellular debris with ingress of erythrocytes, platelets, and inflammatory cells into the media. Associated with medial changes, significant endothelial effects were observed consisting of widening of intercellular boundaries, loss of normal elongated cellular appearance, and the attachment of numerous leukocytes and platelets. During the 10-34-day postdosing period, substantial repair of the arterial lesions occurred such that by day 34 all sections of extramural coronary artery were normal. The lesions induced in the dog are consistent with a hemodynamic effect induced by the pharmacological action of SK&F 95654.
Toxicologic Pathology 24(4):429-35. · 1.91 Impact Factor
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ABSTRACT: The cross-sectional structure of the vasculature is comparatively simple, comprising three layers-the intima, adjacent to the lumen, the media, and the adventitia. Notwithstanding this simplicity, the vessels are host to a variety of reactions to injury. Two cell types, endothelial cells of the intima and smooth muscle cells of the media, are principal targets of damage and repair. The endothelial cells of the intimal layer of the vessel wall present a macromolecular barrier and are important in maintaining vessel integrity. When the integrity is compromised by physical or chemical injury, endothelial cells play a key role in the repair processes. The use of single-cell wound models allows the mechanisms of damage and subsequent repair to be studied in depth. Repair processes can be observed using time-lapse photography and differences between cytoskeleton changes during repair and reendothelialization of small and large wounds can be discriminated. In rats treated with the plant toxin monocrotaline, pulmonary vascular injury occurs which manifests as thrombosis and remodeling with consequent progressive pulmonary hypertension. In vivo and in vitro studies of the mechanism of monocrotaline toxicity suggest that the endothelial cells are an important target. In vitro studies show monocrotaline to be directly cytotoxic; in cells that survive, there are functional changes to the endothelial cells, resulting in a decreased repair capability which may lead to the complex, progressive lung lesions that develop. The other target cells of the vasculature are the smooth muscle cells of the media. Ingestion of primary amines allylamine and β-aminopropionitrile (β-APN) results in chronic vasculotoxicity to the aorta and medium-sized arteries. For allylamine, subtle changes in smooth muscle result in medial hypertrophy and subintimal proliferation. The changes are slow to occur, taking weeks or months of repeated treatment. For β-APN, which is the active ingredient of the toxic sweet pea Lathyrus odoratous, vascular toxicity is manifested by fatal rupture of aortic aneurysms. When these agents are administered concomitantly, a synergistic acute smooth muscle necrosis occurs in large elastic arteries and degenerative changes are seen in muscular arteries. A change in the target for toxicity of allylamine toward the vasculature may be responsible for this synergistic toxic insult. Medial smooth muscle necrosis is also noteworthy after administration of certain pharmaceutical agents of diverse structure and pharmacological activity. These agents induce arteriopathies in dogs and rats, although at different sites. In dogs, the coronary arteries are susceptible, whereas in rats the mesenteric arteries are the principal sites of injury. Since these agents are diverse in structure and biochemical activity, the mechanism of toxicity of these agents appears to be related to their pharmacodynamic activity rather than to a direct effect. Studies on the relationship between vasodilatory and hypotensive properties of these agents and toxic response suggest the mechanism may be related to profound and exaggerated hemodynamic properties.
Toxicology and Applied Pharmacology.
