Short-term toxicity of various pharmacological agents on the in vitro nitrification process in a simple closed aquatic system

in Alternatives to Laboratory Animals [= ATLA] (1999), 27

During the treatment of fish diseases, drugs which inhibit the nitrification process can cause acute ammonia toxicity. The same phenomenon can occur when fish are put into a tank without active cultures ... [more ▼]

During the treatment of fish diseases, drugs which inhibit the nitrification process can cause acute ammonia toxicity. The same phenomenon can occur when fish are put into a tank without active cultures of nitrifying bacteria. The purpose of this study was to quantify the inhibitory effects of 15 pharmacological agents, which are often used as therapeutic agents in ichthyopathology, on ammonia removal and nitrate production in a simple closed aquatic system. The experiments were conducted in polyethylene bags containing activated biofilters and synthetic water solutions, held in a water bath. Ammonia was added to initiate the nitrification process, and graded concentrations of various pharmacological agents were added. The effects of the pharmacological agents on in vitro nitrification were assessed by monitoring ammonia and nitrate concentrations compared to controls with no added agents, for 24 hours. Graded concentrations of ampicillin (Albipen(R)), chloramine T, enrofloxacin (Baytril(R)), erythromycin, levamisole, methylene blue and polymyxin B induced dose-dependent inhibitions of ammonia removal and nitrate production. The corresponding linear regression curves showed high correlation coefficients and were highly significant (p < 0.05). The addition of chloramphenicol, copper (II) sulphate, kanamycin disulphate, malachite green, neomycin sulphate, potassium penicillin G, tetracycline and a mixture of trimethoprim and sulphadoxin (Duoprim(TM)) had no significant effects on the nitrification process. A significant dose-related inhibition of nitrate production, but not of ammonia oxidation, was observed with enrofloxacin. The significant correlation (r = 0.940; p < 0.001) between the degrees of inhibition of ammonia oxidation and nitrate production for the various inhibitory pharmacological agents has also been calculated, with a view to validating this method. The data presented suggest that separate tank facilities for hospitalisation or quarantine are necessary when treating diseased fish with ampicillin, enrofloxacin, chloramine T, erythromycin, levamisole, methylene blue or polymyxin B, in order to avoid ammonia poisoning. [less ▲]

Comparison of Ozone-Induced Effects on Lung Mechanics and Hemodynamics in the Rabbit

in Toxicology and Applied Pharmacology (1998), 150(1), 58-67

The effects of rabbit exposure to ozone (O3)(0.4 ppm for 4 h) on pulmonary mechanical properties and hemodynamics have been investigated on the isolated perfused lung model. Tracheal pressure, airflow ... [more ▼]

The effects of rabbit exposure to ozone (O3)(0.4 ppm for 4 h) on pulmonary mechanical properties and hemodynamics have been investigated on the isolated perfused lung model. Tracheal pressure, airflow, and tidal volume were measured in order to calculate lung resistance (RL) and dynamic compliance (Cdyn). Using the arterial/venous/double occlusion method, the total pressure gradient (deltaPT) was partitioned into four components (arterial, pre-, postcapillary and venous). Dose-response curves to acetylcholine (ACh), substance P (SP), and histamine were constructed in lungs isolated from rabbits immediately or 48 h after air or O3 exposure O3 induced a significant increase in the baseline value of deltaPt, more markedly 48 h after the exposure. Immediately after the exposure, O3 partly inhibited the ACh-, SP-, and histamine-induced decreases in Cdyn and increases in RL. This inhibitory effect was still in part present 48 h after O3 treatment. In the groups studied immediately after exposure, O3 did not significantly modify the ACh-, SP-, and histamine-induced vasoconstriction. Forty-eight hours after exposure, O3 induced a contractile response to ACh and SP in the arterial segment but decreased the response to histamine. We conclude that O3 can induce direct vascular constriction. Directly, but also 48 h after exposure, O3 can inhibit the ACh-, SP-, and histamine-induced changes in lung mechanical properties. Ozone can also induce some changes in the intensity and in the location of the vascular responses to ACh, SP, and histamine. [less ▲]

Biomarqueurs et bioindicateurs chez les vertébrés : importance pour l’évaluation de la santé d’un écosystème

in Annales de Médecine Vétérinaire (1997), 141

Relationship between Parathion and Paraoxon Toxicokinetics, Lung Metabolic Activity, and Cholinesterase Inhibition in Guinea Pig and Rabbit Lungs

in Toxicology and Applied Pharmacology (1996), 138(2), 201-210

Kinetic parameters of parathion and paraoxon uptake were determined in isolated and perfused rabbit and guinea pig lungs. They were related to organophosphate-induced lung cholinesterase inhibition. A ... [more ▼]

Kinetic parameters of parathion and paraoxon uptake were determined in isolated and perfused rabbit and guinea pig lungs. They were related to organophosphate-induced lung cholinesterase inhibition. A single pass procedure was used to perfuse the lungs with an artificial medium perfusate containing paraoxon or parathion. The paraoxon and parathion concentrations were determined in the effluents collected at chosen intervals over an 18-min period beginning at the start of perfusion. Three inflowing concentrations (1 nmol/ml, 10 nmol/ml, and 20 nmol/ml) were tested in guinea pig lungs and one (10 nmol/ml) in rabbit lungs. Cholinesterase activity was determined at time 0 and at the end of the experiment. The lungs abundantly extracted paraoxon and parathion over the perfusion period. The extraction ratio was consistently greater in guinea pig than in rabbit lungs. The uptake velocity varied biexponentially in time, suggesting the existence of two compartments. Initial uptake velocities (A, B) and slopes (alpha and beta) were calculated for both compartments. In guinea pigs, A, B and A + B increased proportionally to the supply rate of paraoxon and parathion while a and b remained constant. No significant difference was observed between parathion and paraoxon uptake kinetics. Parameter B was the only one to differ significantly between the two species (rabbits: 8.19 +/- 1.53 for parathion and 6.85 +/- 1.26 for paraoxon; guinea pigs: 12.75 +/- 0.88 for parathion and 15.02 +/- 3.84 for paraoxon). In the lungs of both species, there was a linear relation between y, the percentage of cholinesterase inhibition induced by either organophosphate, and X, the total amount of drug taken up by the lung tissue (in nmol/g/18 min). The following equations were obtained: y = 0.128 x + 0.979 (R2 = 0.89, p < 0.001 for paraoxon); y = 0.120 x - 6.57 (R2 = 0.82, p < 0.005 for parathion). No difference was observed between the two organophosphates. After treatment with the cytochrome P450 inhibitor piperonyl butoxide, the above relations ceased to apply, but this treatment did not influence the kinetics of paraoxon and parathion uptake. The IC50 value calculated for paraoxon, i.e., the paraoxon concentration required to produce 50% inhibition of lung cholinesterase activity, was similar for guinea pigs (2.22 10(-7) +/- 0.22 M) and rabbits (2.36 10(-7) +/- 0.24 M). In conclusion, the biexponential evolution of the velocity of paraoxon and parathion uptake by the lungs thus demonstrates the presence of two pools. The lower extraction ratios calculated for rabbit lungs reflect the lower initial uptake velocity of the second compartment. In the range of concentrations investigated in guinea pigs, no saturable mechanism could be demonstrated for paraoxon and parathion. Cytochrome P450-related lung metabolic activity, through which parathion is converted to paraoxon, appears as a major step in parathion-induced lung cholinesterase inhibition, although it does not appear to affect parathion toxicokinetics [less ▲]

Modulation of Acetylcholine, Capsaicin and Substance P Effects by Histamine H3 Receptors in Isolated Perfused Rabbit Lungs

in European Journal of Pharmacology (1995), 277(2-3), 243-250

The modulatory role of histamine H3 receptors in pulmonary oedema induced by acetylcholine, capsaicin and by exogenous substance P was investigated in isolated, ventilated rabbit lungs. Endothelial ... [more ▼]

The modulatory role of histamine H3 receptors in pulmonary oedema induced by acetylcholine, capsaicin and by exogenous substance P was investigated in isolated, ventilated rabbit lungs. Endothelial permeability was evaluated by measuring the capillary filtration coefficient (Kf,c). Acetylcholine (10(-8) to 10(-4) M), substance P (10(-10) to 10(-6) M), capsaicin (10(-4) M) and 5-hydroxytryptamine (5-HT) (10(-4) M) induced an increase in the Kf,c. Carboperamide, a novel histamine H3 receptor antagonist, induced a significant leftward shift of the concentration-response curve to acetylcholine and also enhanced the effect of capsaicin on the Kf,c, while it had no significant effect on the response to substance P and 5-HT. Imetit, a new histamine H3 receptor agonist, strongly inhibited the effects of acetylcholine and capsaicin. Imetit also strongly protected the lung against substance P effects but did not prevent the 5-HT-induced increase in the Kf,c. Carboperamide completely blocked the inhibitory effect of Imetit on the acetylcholine response. (R)-alpha-Methylhistamine, an other histamine H3 receptor agonist, had the same protective effect against acetylcholine response as Imetit. We conclude that histamine H3 receptors could protect the lung against acetylcholine- and capsaicin-induced oedema via a prejunctional modulatory effect on the C-fibres. However, since the response to exogenous substance P was also inhibited by histamine H3 receptor stimulation, the presence of such receptors at a postsynaptic level, probably on mast cells, was also suggested. [less ▲]

Mechanisms of Substance P-Induced Pulmonary Oedema in the Rabbit: Interactions between Parasympathetic and Excitatory Nanc Nerves

in Fundamental & Clinical Pharmacology (1995), 9(5), 450-457

The pharmacological mechanisms involved in the substance P (SP)-induced pulmonary oedema were studied in isolated perfused rabbit lungs. Substance P induced a dose-dependent increase in the capillary ... [more ▼]

The pharmacological mechanisms involved in the substance P (SP)-induced pulmonary oedema were studied in isolated perfused rabbit lungs. Substance P induced a dose-dependent increase in the capillary filtration coefficient (Kf,c), responsible for oedema. Atropine, hemicholinium-3 and ruthenium red pretreatment partly protected the lungs against SP effects, while tetrodotoxin and hexamethonium did not significantly modify them. (+/-)CP96,345, a NK1 receptor antagonist, completely inhibited the SP-induced increase in the Kf,c. Like SP, acetylcholine (ACh) and capsaicin also increased the Kf,c. Atropine and (+/-)CP96,345 completely blocked the oedema induced by both drugs. Tetrodotoxin and ruthenium red strongly inhibited the response to capsaicin and acetylcholine. It was concluded that SP-induced pulmonary oedema is in part mediated by a stimulating action on cholinergic efferent nerves, with subsequent release of endogenous acetylcholine. Acetylcholine can, in turn, stimulate the release of SP from excitatory non adrenergic, non cholinergic nerves. The effects induced by capsaicin and exogenous acetylcholine, thus endogenous SP, involve tetrodotoxin-sensitive mechanisms, while those produced by exogenous SP are tetrodotoxin-resistant [less ▲]

Multiple Muscarinic Receptor Subtypes Mediating Pulmonary Oedema in the Rabbit

in Pulmonary Pharmacology (1994), 7(3), 185-193

The effects of various muscarinic antagonists on acetylcholine (ACh)-induced pulmonary oedema were studied in isolated perfused rabbit lungs. ACh induced a dose-dependent increase in the capillary ... [more ▼]

The effects of various muscarinic antagonists on acetylcholine (ACh)-induced pulmonary oedema were studied in isolated perfused rabbit lungs. ACh induced a dose-dependent increase in the capillary filtration coefficient (Kf,c). This effect has been previously related to the activation of the capsaicin-sensitive nerve fibres and the release of substance P. Atropine, pirenzepine (M1-selective antagonist) and 4-DAMP (M3-selective antagonist) altered this response, producing a dose-dependent shift to the right of the ACh concentration-Kf,c response curve. By contrast, the M2-selective antagonist AFDX-116 shifted the ACh concentration-response curve to the left. Atropine, pirenzepine and 4-DAMP also significantly reduced the capsaicin-induced increase in the Kf,c, while AFDX-116 enhanced it. We conclude that multiple muscarinic receptor subtypes are present in the rabbit lung, located on the C-fibres, and are involved in the ACh-induced pulmonary oedema. M1 and M3 receptors seem to stimulate the release of neuropeptides from C-fibres, whereas M2 receptors have an inhibitory effect on these fibers. [less ▲]

Altered Capillary Filtration Coefficient in Parathion- and Paraoxon-Induced Edema in Isolated and Perfused Rabbit Lungs

in Toxicology and Applied Pharmacology (1992), 116(2), 161-169

Changes in pulmonary endothelium permeability and in microvascular hemodynamics induced by parathion (Pth) and paraoxon (Pox), its active metabolite, were investigated in isolated, perfused rabbit lungs ... [more ▼]

Changes in pulmonary endothelium permeability and in microvascular hemodynamics induced by parathion (Pth) and paraoxon (Pox), its active metabolite, were investigated in isolated, perfused rabbit lungs. Blood-free perfusate was recirculated through isolated and ventilated lungs in an isogravimetric state and in zone III conditions. The arterial/venous/double occlusion technique was used to divide the total vascular resistance (Rt) into four components: arterial, precapillary, postcapillary, and venous. The capillary filtration coefficient (Kfc) was evaluated by measuring the amount of fluid filtering through the endothelium when the arterial and venous pressures were suddenly increased. Pth and Pox induced pulmonary edema by increasing endothelium permeability without changing the hemodynamic parameters at any level of the vascular bed. The Kfc value increased progressively, reaching a maximum (Emax) 60 min after administration of organophosphate (558 ± 65% (n = 5) and 707 ± 109% (n = 5) of baseline values, for Pth and Pox, respectively). During the next 60 min, it decreased. The time course of Pox-induced changes in Kfc was similar to that obtained with Pth. The concentration-response curve (Emax) expressed as a percentage of the baseline value versus the logarithm of the malor Pth concentration, ranging from 2 × 10−5 to 4 × 10−4 image) was linear (y = 1661.1 + 327.3x, R = 0.89, p < 0.001, N = 14). Piperonyl butoxide (4 × 10−4 image), an inhibitor of cytochrome P450, had a strong protective effect against Pth (4 × 10−4 image)-induced alterations of endothelium permeability (n = 5, p < 0.001). The effects of Pox (4 × 10−4 image) on Kfc were completely abolished by pretreatment with 10−5 image atropine, as shown by the significantly lower Emax value recorded in atropine-pretreated lungs (129 ± 33%, n = 4) than in Pox-treated lungs (707 ± 109%, n = 5, p < 0.001). The effects of Pth, on the other hand, were only partially inhibited, since the Emax value recorded in atropine-pretreated lungs (196 ± 20%, n = 4) remained significantly higher than that recorded for control lungs (129 ± 15%; n = 5; p < 0.05). These results show that isolated and perfused rabbit lungs constitute and appropriate model for studying the direct pulmonary effects of organophosphates. The edema-inducing action of Pth depends on its activation by conversion to Pox in the lung tissue. It can be explained by an increase in endothelium permeability. This effect is mediated principally by muscarinic receptors [less ▲]