Continuous intravenous infusion of deferoxamine reduces mortality by paraquat in vitamin E-deficient rats.

Paraquat, an oxygen radical-generating agent, is a widely used agrochemical that is also toxic for humans, in whom it may cause respiratory failure. In the present study, we investigated the effect of deferoxamine (DF), an iron chelator with antioxidant capacity, on paraquat toxicity in vitamin E-deficient rats. After the administration of paraquat at a dose of 20 mg/kg the animals were treated with a continuous intravenous infusion of DF for 14 days. In a dose-response study, four of six animals receiving 100 mg DF/kg/24 h survived the study period of 14 days compared with none in the saline-treated control group (n = 6), and three and two animals in the groups receiving 50 (n = 6) and 200 mg DF/kg/24 h (n = 6), respectively. In another series of experiments, animals were monitored for a total period of 35 days, at which time any survivors were killed, and lung histologic examination was carried out. Deferoxamine treatment was started simultaneously (n = 21), 6 h (n = 18), and 16 h (n = 18) after paraquat poisoning. Percent survival in the various time-point groups was 47.7 (p less than 0.01), 38.9 (p less than 0.02), and 22.2 (not significant), respectively, compared with 7.1 (n = 14) in the control group. The presence of lung damage was seen only in those of the surviving rats where DF was started at the 16 h time point after paraquat administration. In ancillary in vitro studies, where Escherichia coli was used as a source of enzymic activity for the redox-cycling of paraquat, DF completely inhibited the formation of hydroxyl radical (.OH).(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative study on the antitumor effect, cardiotoxicity and nephrotoxicity of doxorubicin given as a bolus, continuous infusion or entrapped in liposomes in the Lou/M Wsl rat.

Liposome encapsulation of doxorubicin (DXR) has been shown to increase the therapeutic index of the drug in several animal systems. The prevention of peak plasma concentrations of free drug might be a major factor contributing to the beneficial effects resulting from liposome encapsulation. If so, the administration of DXR as a continuous infusion should also lead to an improved therapeutic index. In the present paper, the administration of liposome-encapsulated DXR is compared with the infusion of DXR with regard to their potential to preserve antitumor activity, enhance survival and reduce cardiomyo- and nephropathy in IgM immunocytoma-bearing Lou/M Wsl rats. Plasma concentrations of DXR were determined to correlate the biological results with pharmacokinetic parameters. Liposomes containing phosphatidylcholine, phosphatidylserine and cholesterol (extrusion-multilamellar vesicles) were used. Bolus injections of free DXR (free DXR) and DXR liposomes (lip-DXR) in a multiple-dose regimen were compared with 24-h infusions of the same cumulative doses of DXR (inf-DXR). The antitumor activity of inf-DXR equalled that of free DXR as well as that of lip-DXR at doses of greater than 0.25 mg/kg. The overall survival of tumor-bearing animals treated with 2.0 mg/kg lip-DXR was significantly prolonged (P less than 0.01) in comparison with that of animals treated with 2.0 mg/kg free DXR; however, treatment with 2.0 mg/kg inf-DXR did not induce a significant prolongation of survival. At a cumulative dose of 12 mg/kg, inf-DXR appeared to be as effective as lip-DXR in reducing the severity of cardiomyopathy induced by free DXR. However, for the reduction of nephropathy, only therapy with lip-DXR was effective. Inf-DXR induced high nephropathy scores comparable with those obtained with free DXR. For the first 24 h after an injection of 2.0 mg/kg or after the start of a continuous infusion of 2.0 mg/kg given over 24 h, similar areas under the plasma concentration-time curves (AUC) were calculated for free DXR and inf-DXR. However, for lip-DXR a much higher value was calculated. The higher plasma levels of lip-DXR did not result in higher cardiac levels. After five daily doses of 2.0 mg/kg, a much lower DXR concentration was found in cardiac tissue after the administration of lip-DXR than after the administration of free DXR or inf-DXR. This suggests that an important parameter to be determined and correlated with biological results is the free (i.e. not bound to liposomes) circulating fraction of DXR in lip-DXR-injected animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Further study of possible direct vascular actions of indapamide in the conduit and renal arteriolar vessels of spontaneously hypertensive rats.

The effect of indapamide on vascular reactivity and its properties as a calcium antagonist were studied in both isolated aorta and perfused renal vasculature of spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats. Indapamide was given orally to SHR and WKY rats for 2 weeks at a dose of 5 mg/kg per day. During this period indapamide did not lower blood-pressure in SHR and WKY rats although there was an adequate concentration of indapamide in the blood. There were no differences observed in the vascular reactivity towards noradrenaline and high-K+ in both the above mentioned vessels in either indapamide- or vehicle-pretreated SHR and WKY rats. Verapamil (10(-9)-10(-5) M) caused a concentration-dependent relaxation of high-K+-depolarized aortas and a decrease in the renal-arteriolar perfusion pressure elevated by high-K+ in both strains of rat. However, indapamide (10(-7)-10(-4) M) did not affect the K+-induced effect on either vessel type. Preloading of the vessels in vivo with indapamide for 2 weeks did not influence the results. In conclusion, further evidence has been presented to show that indapamide does not have calcium-antagonist properties in conduit (aorta) or resistance (renal) vessels under hypertensive conditions. Preloading of the vessels with indapamide was not a prerequisite for the demonstration of a pharmacological action of indapamide.

The potentiation of morphine-withdrawal jumping by clonidine is antagonized by m-chlorophenylpiperazine and not by haloperidol.

Administration of naloxone (0.5 mg/kg i.p.) to morphine-dependent rats induced a strong withdrawal syndrome consisting of body shakes, escape jumping and various autonomic signs. Clonidine (750 micrograms/kg s.c.) had a dual action on naloxone-precipitated withdrawal symptoms in rats: a suppressive action on body shakes and a potentiating action on jumping. Both actions were found to be mediated by alpha 2-receptors which generally are responsible for sedative effects. Therefore, the action of alpha 2-agonists such as clonidine and azepexole was studied more extensively. Since both serotonergic and dopaminergic systems have been suggested to be involved in morphine-withdrawal jumping, the interaction of clonidine and azepexole with serotonergic and dopaminergic drugs was studied. Neither haloperidol (0.3 mg/kg i.p.) nor the benzamides sulpiride (40 mg/kg p.o.) and metoclopramide (8 mg/kg i.p.) affected the jumping potentiated by the alpha 2-agonists. However, the serotonin-agonist m-chlorophenylpiperazine (2.5 mg/kg i.p.) suppressed the effects of clonidine. Precipitation of jumping in morphine-dependent animals was more effective using bremazocine (1.0 mg/kg i.p.). This effect again could be potentiated by clonidine (750 micrograms/kg s.c.). A low dose of m-chlorophenylpiperazine (0.03 mg/kg i.p.) antagonized the clonidine-effect without affecting the basal jumping response. The data suggest that clonidine potentiates naloxone-precipitated jumping by decreasing serotonergic output while the administration of m-chlorophenylpiperazine can counteract this lack of serotonergic activity.

Cardiovascular effects of doxorubicin-induced toxicity in the intact Lou/M Wsl rat and in isolated heart preparations.

Hemodynamic effects were followed for 25 days in conscious nontumor bearing Lou/M Wsl rats during i.v. administration of doxorubicin (DXR) (1 mg/kg) on 5 consecutive days and then weekly. At day 24 cardiac output was significantly reduced in the DXR-treated group (cumulative dose of 7 mg/kg) in comparison with a saline-treated group, suggesting a reduction in myocardial performance. Urethane anesthesia at day 25 depressed cardiac output in control rats whereas this variable was not influenced in DXR-treated rats. Furthermore, blood pressure was significantly higher within DXR-treated rats, suggesting the presence of compensatory mechanisms. Separate experiments 25 days after the first DXR administration (cumulative dose of 7 mg/kg) demonstrated that the inotropic response toward dobutamine or norepinephrine as well as the vasoconstrictor response toward norepinephrine were impaired profoundly, suggesting compensatory mechanisms were functioning within the DXR-treated rats around day 25. In the isolated and perfused rat heart no changes in myocardial contraction under either basal or inotropic stimulatory conditions were observed 24 days after DXR treatment, indicating extracardiac phenomena have to contribute to a reduction in cardiac output and the occurrence of counter regulation mechanisms as observed in the in vivo experiments. However, after a cumulative dose of 11 mg/kg (at day 52), contraction function appeared to be disturbed upon contractility demand by dobutamine in the isolated heart. This observation supports the histological evidence of cardiomyopathy occurring at that time.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of centrally acting adrenergic agonists on temperature and on explorative and motor behaviour. Relation with effects on quasi-morphine withdrawal behaviour.

Seven structurally unrelated adrenergic agonists were compared in three models to measure sedation viz. hole-board exploration, open-field activity and rotarod performance. It appeared that all compounds exerted the same order of potency in these models except for BHT-920 which was more active in the open-field. The other compounds were clonidine, azepexole, guanfacine, lofexidine, UK-14.304 and ST-587. The sedative effect appeared to be not causally related with the hypothermic activity since much higher doses were necessary for the latter effect. There was a relation between the sedative effects and the suppression of body shakes and enhanced locomotor activity induced by dipropylacetate, a potent model for morphine-withdrawal behaviour. The body shakes appeared to be more sensitive than locomotor activity suggesting that the antiwithdrawal action of alpha 2-agonists might be intrinsically higher than their sedative action. The data support earlier findings indicating that the antiwithdrawal action of clonidine is mediated by alpha 2-adrenoceptors.

Reduced cardiotoxicity and nephrotoxicity with preservation of antitumor activity of doxorubicin entrapped in stable liposomes in the LOU/M Wsl rat.

LOU M/Wsl rats inoculated s.c. with 10(4) immunoglobulin immunocytoma cells have a palpable tumor at Day 17. Doxorubicin (DXR) has been entrapped in negatively charged liposomes (lip- DXR) composed of egg phosphatidylcholine, cholesterol, and phosphatidylserine and in positively charged liposomes (lip+ DXR) composed of phosphatidylcholine, cholesterol, and stearylamine. DXR, lip- DXR, and lip+ DXR were administered i.v. (0, 0.25, 0.5, 1.0, and 2.0 mg/kg) at Day 17 for 5 consecutive days and then weekly. Control animals showed progressive tumor growth leading to death 27 days after inoculation. Antitumor activity for all three preparations was dose dependent. DXR and lip- DXR showed the same antitumor activity; lip+ DXR had less antitumor activity. The overall survival of tumor-bearing animals treated with 2.0-mg/kg lip- DXR was significantly prolonged (p less than 0.05) in comparison to the animals treated with 2.0-mg/kg free DXR. Grade III cardiomyopathy was observed 47 days after treatment with free DXR; treatment with lip- DXR resulted in Grade I cardiomyopathy. In animals treated with 1.0-mg/kg and 2.0-mg/kg free DXR urinary albumin concentrations of 10 g/liter were observed. Treatment with 1.0-mg/kg lip- DXR and 1.0-mg/kg lip+ DXR resulted in urinary albumin concentration of less than 3.0 and less than 1.0 g/liter, respectively. Free DXR, 1.0 mg/kg, resulted in a decline of serum albumin concentration from 27.8 +/- 3.2 g/liter to 9.6 +/- 4.2 g/liter. No such decline was observed after treatment with lip- DXR and lip+ DXR. Treatment with a 1.0-mg/kg dose of free DXR resulted in severe glomerular and tubular lesions which were not found after treatment with 1.0-mg/kg lip- DXR and 1.0 mg/kg lip+ DXR. Administration of lip- DXR resulted in lower DXR levels in cardiac and renal tissue compared to administration of free DXR. After administration of lip+ DXR, very low tissue and tumor DXR levels were found. In conclusion, treatment with lip- DXR or lip+ DXR resulted in a prolonged survival, less albuminuria, and higher serum albumin levels. Also, fewer lesions in heart and kidney were found, correlating with lower DXR levels in these organs. Only lip- DXR had the same antitumor effect as free DXR.

A comparative study on possible calcium antagonistic properties of indapamide and other drugs potentially interfering with calcium transport in isolated vascular smooth muscle.

In the present study the effects of indapamide (IN) were compared with those of chlorthalidone (C) and of drugs potentially interfering with calcium transport, e.g. verapamil (V), papaverine (P), phentolamine (PH) and diazoxide (D) using isolated rabbit aorta in order to detect calcium antagonistic properties. IN and C failed to show any relaxation effect towards either noradrenaline (NA)- or high K+-precontracted aorta strips, whereas V and P reduced the K+ contraction dose dependently and PH, V, P and D induced a significant relaxation of the NA contraction. Preincubation with IN or C did not affect the dose-response curve of NA-induced contractions. PH antagonized the NA contraction strongly whereas V and P shifted the dose-response curve to the right only at the highest concentration. In a Ca2+-depleted and high K+-depolarized aorta preincubation with V was able to antagonize Ca2+-induced contraction effectively in a dose-dependent fashion whereas P only showed partial inhibition at the highest concentration. The effects of the drugs on responses to NA in a Ca2+-free medium were also investigated. This type of contraction is likely to be due to mobilization of internally located Ca2+. The results demonstrate that PH was able to counteract this type of contraction effectively whereas only a high concentration of V, P and D was effective in reducing the Na contraction in Ca2+-free medium. Both IN and C failed to affect this type of contraction. In conclusion, the present results indicate that neither IN nor C possess calcium entry and or intracellular calcium antagonistic properties under different conditions as measured in a conduit vessel of rabbits. Moreover, the results point to an additional site of calcium antagonistic action for V, P and D, especially at higher concentrations.

Antitumor effect, cardiotoxicity, and nephrotoxicity of doxorubicin in the IgM solid immunocytoma-bearing LOU/M/WSL rat.

Antitumor activity, cardiotoxicity, and nephrotoxicity induced by doxorubicin were studied in LOU/M/WSL inbred rats each bearing a transplantable solid IgM immunocytoma. Animals with a tumor (diameter, 15.8 +/- 3.3 mm) were treated with iv injections of doxorubicin on 5 consecutive days, followed by 1 weekly injection for 7 weeks (dose range, 0.015-4.0 mg/kg body wt). Tumor regression was observed with 0.5 mg doxorubicin/kg. Complete disappearance of the tumor was induced with 1.0 mg doxorubicin/kg. Histologic evidence of cardiotoxicity scored as grade III was only observed at a dose of 1.0 mg doxorubicin/kg. Light microscopic evidence of renal damage was seen above a dose of 0.5 mg doxorubicin/kg, which resulted in albuminuria and very low serum albumin levels. In the group that received 1.0 mg doxorubicin/kg, the serum albumin level decreased from 33.6 +/- 4.1 to 1.5 +/- 0.5 g/liter. Ascites and hydrothorax were observed simultaneously. The same experiments were performed with non-tumor-bearing rats, in which no major differences were observed. In conclusion, antitumor activity, cardiotoxicity, and nephrotoxicity were studied simultaneously in the same LOU/M/WSL rat. Albuminuria due to renal damage led to extremely low serum albumin levels, so ascites and hydrothorax were not necessarily a consequence of the observed cardiomyopathy.

Protective effects of prostaglandins against ulcerogenic activity of indomethacin during different stages of erosion development in rat stomach. Role of acid and bicarbonate secretion.

Prostaglandin E2 (PGE2) and PGF2 beta decreased the gastric erosive activity of orally administered indomethacin in a dose-dependent manner, when given as a continuous intravenous infusion in the conscious rat. PGE2 protected both during the initial stage of erosion induction and during the later outgrowth to larger erosions. Moreover PGE2 was able to stop the eroding process at any stage as long as the infusion continued. Both PGs were protective only in doses which also reduced the histamine-stimulated acid secretion. PGE2 protected the stomach against indomethacin-induced erosions even in the presence of exogenously administered acid. An infusion of PGE2 stimulated the secretion of bicarbonate in the stomach during some minutes but had no effect during prolonged infusion. These results suggest that, although effects on secretion of acid and bicarbonate were found, these effects cannot be the (only) explanation for the cytoprotective effects observed. Furthermore the protective effect of PGE2 is not confined to any specific stage of the development of indomethacin-induced gastric injury.

The influence of paracetamol on the anti-inflammatory, the anti-pyretic and the analgesic activity of indomethacin.

Interactions between indomethacin (INDO) and paracetamol (PAR) with regard to their anti-inflammatory, anti-pyretic and analgesic activities were studied in rats. The anti-inflammatory and anti-pyretic effects of INDO and PAR were additive. Although antagonism was observed in the analgesic test, the effect of the combination was not inferior to that of PAR alone.

Etomidate-anaesthesia, with and without fentanyl, compared with urethane-anaesthesia in the rat.

In spontaneously breathing rats, continuous infusion of etomidate with and without fentanyl caused a slight decrease in blood pressure and heart rate. Coadministration of fentanyl and etomidate in order to obtain full anaesthesia and analgesia resulted in respiratory depression. In artificially ventilated rats both etomidate as well as the anaesthetic combination caused a strong reduction in aortic flow and an increase in total peripheral resistance. A single infusion of etomidate did not change blood pressure. Etomidate combined with fentanyl reduced blood pressure. Under adjusted ventilation blood pressure, aortic flow, max(dF/dt) and heart rate were progressively reduced during a 4 h period. In contrast, urethane anaesthesia reduced aortic flow to a minor extent. Total peripheral resistance and max(dF/dt) were hardly affected. The slightly reduced blood pressure and blood gas variables remained stable during the experiment. From pharmacokinetic studies it was established that effective etomidate plasma levels were maintained constant during the experimental period. Pharmacokinetic interaction between etomidate and fentanyl did not occur. It is concluded that for anaesthesia of longer duration during cardiovascular experiments in rats, urethane is preferable to etomidate/fentanyl because it does not cause serious changes in basal haemodynamic variables.

Dipropylacetate-induced quasi-morphine abstinence behaviour in the rat: suppression by alpha 2-adrenoceptor stimulation.

The anti-withdrawal effect of clonidine was studied using quasi-morphine abstinence behaviour induced by dipropylacetate (DPA) in naive rats. Clonidine potently suppressed body shakes and locomotor activity (ID50 30 and 40 micrograms/kg IP respectively). Phenoxybenzamine and prazosine did not antagonize the anti-withdrawal effect of clonidine, whereas piperoxane and yohimbine were effective with respect to locomotor activity and a total abstinence score. Piperoxane also reversed the suppressive action of clonidine on body shakes. Other alpha 2-agonists (guanfacine, azepexole and BHT 920) also suppressed DPA-induced behaviour, whereas the lipophilic alpha 1-agonist ST-587 had such an effect only at high doses. The relative potencies of the alpha 2-agonists correlated well with their potency to exert other alpha 2-adrenoceptor mediated actions such as blood pressure lowering and sedation.

Een onderzoek naar de aanwezigheid van amodiaquine in de urine na orale toediening / A research into the presence of amodiaquine in the urine after oral administration

Amodiaquine (Camoquin R) is an antimalarial, that belongs to the group of 4-aminoquinoline-derivates. Since 1968 it is being used in the Surinamese battle against malaria. In the Surinamese interior, ADQ (Amodiaquine) is administered as an additive to kitchen-salt, in a concentration of 0,4 per cent (WHO/Mem/l, 1960). To obtain an impression of the presence of ADQ in the urine, an attempt has been made to put up a laboratory determination. The relation between the presence of ADQ in consumed salt, and the occurrence in urine, had to be determined up to a concentration of 1/10000 M. Some inhabitants of the area around the Upper-Suriname river were examined, but ADQ was found in none of them. These negative results are probably due to a different kinetic behaviour of ADQ than that of Chloroquine

1-Hydroxy-3-amino-pyrrolidone-2(HA-966): a new GABA-like compound, with potential use in extrapyramidal diseases.

1. The drug HA-966 (1-hydroxy-3-amino-pyrrolidone-2), which chemically resembles the cyclic form of GABA, has been studied for neuro-pharmacological properties and for effects on the catecholamine content of the corpus striatum.2. The acute effects on spontaneous behaviour of rodents included flaccid catalepsy and reversible tranquillization in doses which were 5% or less of the lethal dose. Long lasting depression of the CNS, followed by complete recovery, was produced in the cat and the dog. In the monkey HA-966 caused periodical sleeping episodes.3. The exploratory behaviour and the amphetamine-induced motor activity in mice were blocked by HA-966. The toxicity of amphetamine in aggregated mice was only moderately reduced, suggesting that HA-966 differs from neuroleptics.4. Tremors induced by chemical agents (nicotine, zinc and tremorine) were markedly inhibited by HA-966. The muscarinic effects of tremorine were not reduced by HA-966, indicating a selective central antitremor effect.5. HA-966 elevated the threshold to strychnine convulsions and abolished the ipsilateral flexor reflex, while not having motor endplate blocking properties. It is suggested that HA-966 depresses central internuncial neurones.6. In rats and rabbits HA-966 produced synchronous EEG and inhibited the sensory arousal in doses not causing sedation. In the monkey the drug caused a periodical dissociation between ;sleep-EEG' and behaviour.7. In rat brain, HA-966 selectively elevated the dopamine content in the corpus striatum, while no changes in noradrenaline and 5-hydroxytryptamine contents could be demonstrated. The effect was still present when dopa synthesis was inhibited with alpha-methyl-p-tyrosine.8. Several effects of intravenously administered HA-966 became manifest after an appreciable delay and in hepatectomized mice the effects were much reduced. It is postulated that HA-966 is converted to a pharmacologically active metabolite.9. The results are discussed in the light of current views on drug therapy in extrapyramidal conditions and a GABA-related hypothesis as to the mode of action of HA-966 is presented.