Cardiac remodeling and MMPs on the model of chronic daunorubicin-induced cardiomyopathy in rabbits.

The matrix metalloproteinases (MMPs) play a key role during cardiac remodeling. The aim of the study was to investigate the changes in collagenous proteins and MMPs in the model of non-ischemic, anthracycline-induced chronic cardiomyopathy in rabbits using both biochemical and histological approaches. The study was carried out in three groups of Chinchilla male rabbits: 1) daunorubicin (3 mg/kg, once weekly for 10 weeks), 2) control (saline in the same schedule), 3) daunorubicin with the cardioprotectant dexrazoxane (60 mg/kg, before each daunorubicin). Morphological changes in the myocardium of daunorubicin-treated animals were characterized by focal myocardial interstitial fibrosis of different intensity. The subsequent proliferation of the fibrotic tissue was marked by an increased content of both collagen types I and III, which resulted in their typical coexpression in the majority of bundles of fibers forming either smaller or larger scars. Biochemical analysis showed a significantly increased concentration of hydroxyproline, mainly in the pepsin-insoluble fraction of collagenous proteins, in the daunorubicin-treated group (1.42+/-0.12 mg/g) as compared with the control (1.03+/-0.04 mg/g) and dexrazoxane (1.07+/-0.07 mg/g) groups. Dexrazoxane co-administration remarkably reduced the cardiotoxic effects of daunorubicin to the extent comparable with the controls in all evaluated parameters. Using zymography, it was possible to detect only a gelatinolytic band corresponding to MMP-2 (MMP-9 activity was not detectable). However, no significant changes in MMP-2 activity were determined between individual groups. Immunohistochemical analysis revealed increased MMP-2 expression in both cardiomyocytes and fibroblasts. Thus, this study has revealed specific alterations in the collagen network in chronic anthracycline cardiotoxicity in relationship to the expression and activity of major MMPs.

Dexrazoxane-afforded protection against chronic anthracycline cardiotoxicity in vivo: effective rescue of cardiomyocytes from apoptotic cell death.

BACKGROUND: Dexrazoxane (DEX, ICRF-187) is the only clinically approved cardioprotectant against anthracycline cardiotoxicity. It has been traditionally postulated to undergo hydrolysis to iron-chelating agent ADR-925 and to prevent anthracycline-induced oxidative stress, progressive cardiomyocyte degeneration and subsequent non-programmed cell death. However, the additional capability of DEX to protect cardiomyocytes from apoptosis has remained unsubstantiated under clinically relevant in vivo conditions. METHODS: Chronic anthracycline cardiotoxicity was induced in rabbits by repeated daunorubicin (DAU) administrations (3 mg kg(-1) weekly for 10 weeks). Cardiomyocyte apoptosis was evaluated using TUNEL (terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling) assay and activities of caspases 3/7, 8, 9 and 12. Lipoperoxidation was assayed using HPLC determination of myocardial malondialdehyde and 4-hydroxynonenal immunodetection. RESULTS: Dexrazoxane (60 mg kg(-1)) co-treatment was capable of overcoming DAU-induced mortality, left ventricular dysfunction, profound structural damage of the myocardium and release of cardiac troponin T and I to circulation. Moreover, for the first time, it has been shown that DEX affords significant and nearly complete cardioprotection against anthracycline-induced apoptosis in vivo and effectively suppresses the complex apoptotic signalling triggered by DAU. In individual animals, the severity of apoptotic parameters significantly correlated with cardiac function. However, this effective cardioprotection occurred without a significant decrease in anthracycline-induced lipoperoxidation. CONCLUSION: This study identifies inhibition of apoptosis as an important target for effective cardioprotection against chronic anthracycline cardiotoxicity and suggests that lipoperoxidation-independent mechanisms are involved in the cardioprotective action of DEX.

Anthracycline toxicity to cardiomyocytes or cancer cells is differently affected by iron chelation with salicylaldehyde isonicotinoyl hydrazone.

BACKGROUND AND PURPOSE: The clinical utility of anthracycline antineoplastic drugs is limited by the risk of cardiotoxicity, which has been traditionally attributed to iron-mediated production of reactive oxygen species (ROS). EXPERIMENTAL APPROACH: The aims of this study were to examine the strongly lipophilic iron chelator, salicylaldehyde isonicotinoyl hydrazone (SIH), for its ability to protect rat isolated cardiomyocytes against the toxicity of daunorubicin (DAU) and to investigate the effects of SIH on DAU-induced inhibition of proliferation in a leukaemic cell line. Cell toxicity was measured by release of lactate dehydrogenase and staining with Hoechst 33342 or propidium iodide and lipid peroxidation by malonaldehyde formation. KEY RESULTS: SIH fully protected cardiomyocytes against model oxidative injury induced by hydrogen peroxide exposure. SIH also significantly but only partially and with no apparent dose-dependency, reduced DAU-induced cardiomyocyte death. However, the observed protection was not accompanied by decreased lipid peroxidation. In the HL-60 acute promyelocytic leukaemia cell line, SIH did not blunt the antiproliferative efficacy of DAU. Instead, at concentrations that reduced DAU toxicity to cardiomyocytes, SIH enhanced the tumoricidal action of DAU. CONCLUSIONS AND IMPLICATIONS: This study demonstrates that iron is most likely involved in anthracycline cardiotoxicity and that iron chelation has protective potential, but apparently through mechanism(s) other than by inhibition of ROS-induced injury. In addition to cardioprotection, iron chelation may have considerable potential to improve the therapeutic action of anthracyclines by enhancing their anticancer efficiency and this potential warrants further investigation.

Evaluation of ECG time intervals in a rabbit model of anthracycline-induced cardiomyopathy: a useful tool for assessment of cardioprotective agents.

The aim of this study was to analyze the ECG time intervals in the course of the development of chronic anthracycline cardiomyopathy in rabbits. Furthermore, this approach was employed to study the effects of a model cardioprotective drug (dexrazoxane) and two novel iron chelating compounds--salicylaldehyde isonicotinoyl hydrazone (SIH) and pyridoxal 2-chlorobenzoyl hydrazone (o-108). Repeated daunorubicin administration induced a significant and progressive prolongation of the QRS complex commencing with the eighth week of administration. At the end of the study, we identified a significant correlation between QRS duration and the contractility index dP/dt(max) (r = -0.81; P<0.001) as well as with the plasma concentrations of cardiac troponin T (r = 0.78; P<0.001). In contrast, no alterations in ECG time intervals were revealed in the groups co-treated with either dexrazoxane or both novel cardioprotective drugs (SIH, o-108). Hence, in this study, the QRS duration is for the first time shown as a parameter suitable for the non-invasive evaluation of the anthracycline cardiotoxicity and cardioprotective effects of both well established and investigated drugs. Moreover, our results strongly suggest that novel iron chelators (SIH and o-108) merit further study as promising cardioprotective drugs against anthracycline cardiotoxicity.

Early detection of anthracycline cardiotoxicity in a rabbit model: left ventricle filling pattern versus troponin T determination.

Anthracycline cardiotoxicity represents a serious risk of anticancer chemotherapy. The aim of the present pilot study was to compare the potential of both the left ventricular (LV) filling pattern evaluation and cardiac troponin T (cTnT) plasma levels determination for the early detection of daunorubicin-induced cardiotoxicity in rabbits. The echocardiographic measurements of transmitral LV inflow as well as cTnT determinations were performed weekly for 10 weeks in daunorubicin (3 mg/kg weekly) and control groups (n=5, each). Surprisingly, no significant changes in LV-filling pattern were observed through the study, most likely due to the xylazine-containing anesthesia, necessary for appropriate resolving of the E and A waves. In contrast to the echographic measurement, the dP/dt(min) index obtained invasively at the end of the study revealed a significant impairment in LV relaxation, which was further supported by observed disturbances in myocardial collagen content and calcium homeostasis. However, at the same time cTnT plasma levels were progressively rising in the daunorubicin-treated animals from the fifth week (0.024+/-0.008 microg/l) until the end of the experiment (0.186+/-0.055 microg/l). Therefore, in contrast to complicated non-invasive evaluation of diastolic function, cTnT is shown to be an early and sensitive marker of anthracycline-induced cardiotoxicity in the rabbit model.

Safety and tolerability of repeated administration of pyridoxal 2-chlorobenzoyl hydrazone in rabbits.

Recently, pyridoxal 2-chlorobenzoyl hydrazone (o-108) has been identified as an effective iron chelator [Link et al., Blood 2003; 101: 4172-79]. Since chronic treatment would be necessary in its potential indications, in the present study, the safety and tolerability of this agent after repeated administration was determined. Three doses of o-108 (25, 50, 100 mg/kg, in 10% Cremophor EL) were administered intraperitoneally, once weekly, for 10 weeks to three groups (n=5 each) of Chinchilla male rabbits. The effects on biochemical, haematological and cardiovascular parameters were examined during the experiment; histopathological examination was performed at the end of the experiment. Results were compared with control (saline 2 mL/kg, n=11) and vehicle groups (10% Cremophor EL, 2 mL/kg, n=12). No premature deaths occurred; the well-being of animals was evidenced by their body weight gain, although lower gain was observed with the highest dose (100 mg/kg). Significant elevations of cardiac troponin T plasma concentrations were observed with the highest dose of o-108, but no abnormalities were found in the cardiovascular function and only minor and inconsistent changes in haematological and biochemical parameters were observed. Histopathological examinations of selected organs revealed only weak and reversible changes through all studied groups. Thus, the data from this study suggest that o-108 remains a promising drug from the standpoint of the possibility of its repeated administration and warrants further investigation.

Study of daunorubicin cardiotoxicity prevention with pyridoxal isonicotinoyl hydrazone in rabbits.

Risk of cardiotoxicity is the most serious drawback of the clinical usefulness of anthracycline antineoplastic antibiotics, which however, remain among the most powerful and widely employed anticancer drugs. In this study we have used daunorubicin-induced cardiomyopathy in rabbits as a model to investigate possible cardioprotective effects of pyridoxal isonicotinoyl hydrazone (PIH)-a principal representative of a novel group of aroylhydrazone iron chelators. Three groups of animals were used: a control group (n=11; i.v. saline), daunorubicin-treated animals (n=11; 3mg/kg, i.v.), and animals pretreated with PIH (n=9, 25 mg/kg, i.p.) 60 min before daunorubicin administration. All substances were administered once weekly for 10 weeks. Repeated administration of daunorubicin caused premature death in four animals and induced conspicuous histopathological changes in the myocardium, progressive and significant impairment of systolic heart function (a decrease in left ventricular dP/dt(max), ejection fraction, an increase in the pre-ejection period/left ventricular ejection time index), and a gradual increase in cardiac troponin T plasma concentrations. On the contrary, all the PIH-treated animals have survived all daunorubicin applications. Furthermore, in this group, the daunorubicin-induced cardiac changes were in most functional, biochemical as well as morphological parameters less pronounced than in the group receiving daunorubicin alone. Hence, PIH and other aroylhydrazones merit further investigation as potentially protective agents against anthracycline-induced cardiotoxicity.

The effect of new lipophilic chelators on the activities of cytosolic reductases and P450 cytochromes involved in the metabolism of anthracycline antibiotics: studies in vitro.

A major obstacle to the therapeutic use of anthracyclines, highly effective anticancer agents, is the fact that their administration results in dose-dependent cardiomyopathy. According to the currently accepted hypothesis, anthracyclines injure the heart by generating oxygen free radicals. The ability of pyridoxal isonicotinoyl hydrazone (PIH) and salicylaldehyde isonicotinoyl hydrazone (SIH) -- new iron chelators -- to protect against peroxidation as well as their suitable biological, physical and chemical properties make the compounds promising candidates for pre-clinical and clinical studies. Activities of carbonyl reductase CR (1.1.1.184), dihydrodiol dehydrogenase DD2 (1.3.1.20), aldehyde reductase ALR1 (1.1.1.2) and P450 isoenzymes (CYP1A1, CYP1A2, CYP2B, CYP3A) involved in the metabolism of daunorubicin, doxorubicin and other drugs or xenobiotics were studied. Various concentrations of the chelators were used either alone or together with daunorubicin or doxorubicin for in vitro studies in isolated hepatocytes. A significant decrease of activity was observed for all enzymes only at PIH and SIH concentrations higher than those presumed to be used for therapy. The results show that PIH and SIH have no effect on the activities of the enzymes studied in vitro and allow us to believe that they will not interfere with the metabolism of co-administered drugs and other xenobiotics. Daunorubicin (Da) and doxorubicin (Dx) significantly reduce cytochrome P450 activity, but the addition of SIH and PIH chelators (50 microM) reverses the reduction and restores the activity to 70-90 % of the activity of relevant controls.

Protein profiling in daunorubicin-induced cardiomyopathy.

The aim of this paper was to study the protein remodelling of the left ventricle following repeated administration of either daunorubicin (DNR) or DNR in combination with the cardioprotective agent dexrazoxane (DXZ). The experiment was carried out on three groups of Chinchilla male rabbits: 1. DNR (3 mg/kg i.v.), 2. DNR (3 mg/kg i.v.) + DXZ (60 mg/kg i.p.), and 3. the control group (saline 1 ml/kg i.v. in the same schedule). The drugs were given once weekly, max. 10 administrations. Protein fractions were isolated by stepwise extraction from the samples of the left ventricle. In the DNR-group, the concentrations of both, metabolic and contractile proteins were significantly reduced, while the amount of collagen was significantly higher in comparison with the control group. In the group treated with DNR and DXZ, the concentrations of individual protein fractions (except metabolic proteins) were comparable to those of the control group, which confirms a significant cardioprotective effect of DXZ. The changes of protein profiling corresponded to functional examination of both cardiac parameters (EF, dP/dt(max), PEP: LVET index) and histological examination. These data should be used in further studies dealing with evaluation of cardiotoxic and, possibly, cardioprotective effects of new drugs.

Cardiac troponin T following repeated administration of pyridoxal isonicotinoyl hydrazone in rabbits.

Pyridoxal isonicotinoyl hydrazone (PIH) is a new tridentate Fe-chelating agent that should be very promising in many pathological states resulting from both an iron-overload and formation of free radicals. The aim of our study was to investigate the effect of PIH on the cardiovascular system focusing to the regulatory protein -- cardiac troponin T (cTnT). The study was carried out in two groups of Chinchilla male rabbits: 1) PIH (50 mg/kg dissolved in 10 % Cremophor i.p., once a week, 10 administrations, n=8) and 2) Cremophor (2 ml/kg i.p. in the same schedule, n=7). Plasma concentrations of cTnT (as a marker of myocardial damage) were measured using a commercial kit (Roche). cTnT was within the physiological range (i.e. < 0.1 microg/l) during the whole experiment in the Cremophor group. In the PIH group, the cTnT levels were not significantly increased when compared with the control group or with the initial values (except with those before the 5th administration). Furthermore, we analyzed the cytosolic and myofibrillar fraction of cTnT in the left ventricular myocardium. Using SDS-PAGE and Western blot we resolved three isoforms. The profiling of TnT did not differ significantly between the PIH-treated group and the Cremophor-treated group. Our data concerning cTnT support the opinion that the possible cardiotoxicity of PIH is very low.

[Plasma levels of troponin T in rabbits after administration of new antineoplastic agents (Oracin and Dimefluron) and daunorubicin]. / Plazmatické hladiny troponinu T u králíku po podání nových antineoplastických látek (Oracinu a Dimefluronu) s daunorubicinem.

Recently, cardiac troponin T (cTnT) has been shown to be a sensitive marker of anthracycline-induced cardiomyopathy. In our study, the cardiotoxicity of repeated i.v. administration (once a week, 10 administrations) of daunorubicin combined with new antineoplastic drugs (with mild side-effects) were followed in two groups of rabbits: 1) Dimefluron (3,9-dimethoxybenfluron hydrochloride-12 mg/kg) + daunorubicin (3 mg/kg), 2) Oracin (6-[2-(2-hydroxyethyl)aminoethyl]-5,11-dioxo-5,6-dihydro-11H- indeno[1,2c]isoquinoline hydrochloride--10 mg/kg) + daunorubicin (3 mg/kg) and compared with the control group (saline--1 ml/kg) and the group with experimentally induced cardiomyopathy (daunorubicin--3 mg/kg). The concentration of cTnT in heparinized plasma samples was measured using commercial kit (Roche). In the control group, plasma levels of cTnT were always within the physiological range (i.e. lower than 0.1 microgram/l) during the experiment. During the development of daunorubicin-induced cardiomyopathy, after the eighth administration of drug, cTnT was significantly higher (0.31 +/- 0.11 microgram/l) in animals with premature deaths compared with the rest of the group (0.04 +/- 0.03 microgram/l). The animals with pathological values of cTnT were at higher risk of premature deaths (P = 0.0006). The combination of daunorubicin either with Oracin or with Dimefluron caused neither significant changes of cTnT levels nor significant deterioration of other followed-up parameters (especially, functional and toxicological parameters). Similarly to the daunorubicin group, the animals with pathological levels of cTnT after the eighth administration of antineoplastic drugs were at higher risk of premature death (P = 0.025). Our results show that the plasma concentration of cardiac troponin T could be a suitable predictive marker of cardiotoxicity of antineoplastic drugs.

Anthracycline-induced cardiotoxicity.

Anthracycline antibiotics are among the most effective and widely used antineoplastic drugs. Their usefulness is limited by a cumulative dose-related cardiotoxicity, whose precise mechanisms are not clear as yet. The principal role is possibly exerted by free oxygen radicals generated by "redox-cycling" of anthracycline molecule and/or by the formation of anthracycline-ferric ion complexes. The iron catalyzes the hydroxyl radical production via Haber-Weiss reaction. The selective toxicity of ANT against cardiomyocytes results from high accumulation of ANT in cardiac tissue, appreciable production of oxygen radicals by mitochondria and relatively poor antioxidant defense systems. Other additional mechanisms of the anthracycline cardiotoxicity have been proposed--calcium overload, histamine release and impairment in autonomic regulation of heart function. The currently used methods for an early identification of anthracycline cardiotoxicity comprise ECG measurement, biochemical markers, functional measurement and morphologic examination. Among a plenty of studied cardioprotective agents only dexrazoxane (ICRF-187) has been approved for clinical use. Its protective effect likely consists in intracellular chelating of iron. However, in high doses dexrazoxane itself may cause myelotoxicity. This fact encourages investigation of new cardioprotectants with lower toxicity. Orally active iron chelators and flavonoids attract more attention. Modification of dosage schedule and synthesis of new anthracycline analogues may represent alternative approaches to mitigate anthracycline cardiotoxicity while preserving antitumour activity.

[Effects of new antineoplastic agents (dimethoxybenflurone and Oracin) on the cardiovascular system and other parameters in the rabbit in vivo]. / Ucinky nových antineoplastických látek (dimethoxybenfluronu a Oracinu) na kardiovaskulární systém a dalsí parametry u králíku in vivo.

Anthracycline derivatives belong among the most effective antineoplastic drugs but their therapeutic use is limited by their side effects--a dose-related cardiotoxicity. The influence of repeated i.v. administration (once weekly, max. 10 weeks) of new antineoplastic agents--dimethoxybenfluron (DMB) (3,9-dimethoxybenfluron hydrochloride, C23H24O4NCl, M.w. 413.9, Institute of Experimental Biopharmaceutics, Czech Academy of Sciences, Hradec Králové, Czech Republic; 12 or 24 mg base/kg) and Oracin (6-[2-(2-hydroxyethyl)aminoethyl]-5,11-dioxo-5,6-dihydro-11H- indeno[1,2c]isoquinoline hydrochloride), C20H19N2O3Cl, M.w. 370.84, Research Institute for Pharmacy and Biochemistry, Prague, Czech Republic; 5 or 10 mg/kg) on cardiovascular, biochemical, haematological and histological parameters were studied in rabbits in vivo. Data obtained in these groups were compared with the group with experimentally induced cardiomyopathy (daunorubicin 50 mg/m2 i.v.) and with the control group (saline 1 ml/kg). Only mild and mostly no significant changes of the cardiovascular parameters (DMB 12 group: PEP:LVET ratio--0.408-0.502, LV dP/dtmax.--1337.0 kPa/s; DMB 24 group: PEP:LVET ratio--0.407-0.433, LV dP/dtmax.--1438.2 kPa/s), biochemical parameters (decrease in natrium, ALP and increase in glucose, GPX and GSH levels) and haematological parameters (increase in erythrocytes and decrease in leukocytes after the larger dose of the drug) were found in the dimethoxybenfluron groups. Repeated administration of the lower dose of Oracin induced only mild and mostly no significant changes of parameters (PEP:LVET ratio--0.393-0.475, LV dP/dtmax.--1092.4 kPa/s) in comparison with the control group. Though significant in some intervals, only a mild oscillation of the PEP:LVET ratio (0.368-0.446), decrease in LV dP/dtmax. (991.2 kPa/s) and--in comparison with control group--significantly higher blood pressure and lower heart rate were found after the higher dose of Oracin. In the most of haematological and biochemical parameters (with the exception of chlorides, protein and albumin levels) no significant changes were present. Histological examination of the heart revealed normal structure of the myocardium including minute changes of myocardium following administration of antineoplastic agents in all groups. Administration of new antineoplastic agents induced mostly mild changes of the followed-up parameters (PEP:LVET ratio, LV dP/dtmax., heart rate, levels of cardiac troponin T, survival of animals, haematological and biochemical parameters); the values of parameters were mostly significantly different from those in rabbits with daunorubicin-induced cardiomyopathy. On the basis of our results it is possible to conclude that the administration of dimethoxybenflurone and Oracin did not induce signs of cardiotoxicity in rabbits in vivo. This observation is considered to be important from the viewpoint of possible further clinical use of these new antineoplastic agents.

Cardiac troponin T as a marker of myocardial damage caused by antineoplastic drugs in rabbits.

Anthracycline derivatives are among the most effective antineoplastic drugs but their therapeutic use is limited by their adverse effects. The cardiac side-effects of antineoplastic drugs were investigated in rabbits in vivo from the viewpoint of release of cardiac troponin T (cTnT) measured by Elecsys Troponin T STAT immunoassay (Boehringer Mannheim, Germany). No increase in cTnT was found following administration of a single dose of daunorubicin (3 mg/kg i.v., n = 4). During development of daunorubicin-induced cardiomyopathy (daunorubicin 3 mg/kg i.v., once a week; maximum nine administrations, n = 7), the levels of cTnT were within the physiological range (i.e. cTnT <0.1 microg/l) at the beginning of the experiment and before and after the 5th administration, but the pathological values of cTnT after the 8th administration in 43% animals (0.22+/-0.08 microg/l) correlated with their premature death. In the control group, the levels of cTnT were always lower than 0.1 microg/l during the experiment. Following administration of a new antineoplastic drug - Oracin [6-[2-(2-hydroxyethyl) aminoethyl]-5,11-dioxo-5,6-dihydro-11H-indeno [1,2-c]-isoquinoline hydrochloride, 10 mg/kg i.v., once weekly, ten administrations, n = 7], there was no increase in cTnT levels. These findings correlated with the PEP: LVET index, histological examination and no animal succumbing to premature death. It is possible to conclude that cTnT is a useful marker for the prediction of experimentally induced anthracycline cardiomyopathy and for the evaluation of cardiotoxic (and, possibly, cardioprotective) effects of new drugs in rabbits.

IGF-I in experimental daunorubicin-induced cardiomyopathy in rabbits.

1. The occurrence of IGF-I was investigated in rabbits with experimentally daunorubicin-induced cardiomyopathy. IGF-I was measured in the heart, serum, liver and skeletal muscle. 2. A significant increase in the IGF-I was found in the left heart ventricle in daunorubicin cardiomyopathy (152.9 +/- 10.0 ng/g vs 95.1 +/- 4.2 ng/g in the control group). This site of increased IGF-I activity corresponded well with the maximum of morphological changes (dispersed cytolysis of cardiomyocytes mostly without developed subsequent interstitial myofibrosis). 3. The highest levels of IGF-I were present in right and left cardiac atrium (but without significant differences between the groups). Furthermore, in skeletal muscle, the levels of IGF-I in the daunorubicin group (839.0 +/- 142.1 ng/g) were significantly higher in comparison with the control group (482.5 +/- 83.1 ng/g). 4. The level of IGF-I in the left ventricle in the daunorubicin group (but not in the control group) was significantly higher than that in the liver. There were no correlations observed between the levels of IGF-I in the heart and in the serum. 5. The increase in IGF-I concentrations in the left heart ventricle after the administration of daunorubicin may thus reflect possible autocrine/paracrine role of IGF-I in cardiomyopathy.

The influence of dimethoxybenfluron on biochemical and haematological parameters in rabbits.

The influence of repeated i.v. administration of dimethoxybenfluron (NO-1-B) (12 or 24 mg base/kg once weekly, 10 weeks) on biochemical and haematological parameters were studied in rabbits in vivo. No significant changes were mostly found in the serum ion levels between the dimethoxybenfluron and the control groups, as well as in most of other biochemical parameters (including total protein and albumin levels). Nevertheless, the lower dose of dimethoxybenfluron caused an increase in the glucose level. Furthermore, no significant changes were mostly present also in haematological parameters in the dimethoxybenfluron groups of rabbits (a mild decrease in thrombocytes and leucocytes). The results of our study support an assumption of good tolerance of dimethoxybenfluron from the viewpoint of its influence on biochemical and haematological parameters in rabbits and may be considered of importance for a possible therapeutic use of the derivatives.

Cholinesterases in dexrazoxane-treated daunorubicin cardiomyopathy in rabbits.

Changes in cholinesterases activities in daunorubicin cardiomyopathy and in dexrazoxane (DRZX)-treated daunorubicin cardiomyopathy were investigated in rabbits. Acetyl- and butyrylcholinesterase (AChE and BuChE) were determined using Ellman's method. In the serum, a significant decrease of BuChE was observed in the daunorubicin group (9.05 at the beginning and 7.15 microcat/l at the end of the experiment). After DRZX, no significant changes were found and a significant increase in BuChE was observed in the control group (10.26-12.38 microcat/l). AChE activity in the left and right cardiac ventricles was not significantly different between the groups while in the septum there was a significantly lower AChE activity found in the daunorubicin group only. BuChE activity was significantly decreased in the left (15.64 ncat/g) and right (19.27 ncat/g) heart ventricles, in the septum and in the liver in the daunorubicin group. A significant decrease in serum total protein and albumin was demonstrated only in the daunorubicin group. Our results support the hypothesis about the influence of daunorubicin on protein (and enzyme) synthesis in the liver and heart. A protective effect of DRZX on cholinesterases activity was observed. The changes in cholinesterase activities may thus reflect their possible role in cardiomyopathy.

Myocardial elements content and cardiac function after repeated i.v. administration of DMPS in rabbits.

1. A dithiol chelating agent--2,3-dimercapto-1-propanesulphonate (DMPS)--may be administered in acute or chronic intoxication with certain heavy metals (e.g. cadmium, cobalt, lead) that may cause cardiotoxicity. 2. DMPS can act as a depleter of physiologically important elements (e.g. potassium, magnesium, calcium) in various tissues including cardiac one. The possibility of subsequent alteration in cardiac function cannot be excluded. 3. Changes in the myocardial concentration of the above mentioned elements at the end of the experiment and cardiac function were studied during repeated i.v. administration of DMPS as single doses of 50 mg/kg/ week for 10 weeks in rabbits. Biochemical, haematological and histological examinations were also performed. 4. Most of the measured parameters were not affected by the repeated administration of DMPS. A significant decrease in magnesium and a near significant decrease in calcium in cardiac muscle was not accompanied by functional or morphological changes. It is still suggested, however, that care should be taken in using DMPS for treating patients with cardiotoxicity as a result of poisoning with heavy metals.

Effects of repeated administration of dithiol chelating agent--sodium 2,3-dimercapto-1-propanesulphonate (DMPS)--on biochemical and haematological parameters in rabbits.

The effects of weekly intravenously administered a dithiol chelating agent-sodium 2,3-dimercaptopropane-sulphonate (DMPS)-in a single dose of 50 mg/kg/week for 10 weeks on biochemical and haematological parameters were studied in rabbits. DMPS was well tolerated, an increase in body weight was similar in the DMPS-treated and control animals. DMPS caused significant decrease in plasma calcium and vitamin E concentrations at the end of the experiment. No significant differences in haematological parameters between the DMPS and control groups were observed. A significant decrease in magnesium content in myocardial tissue was observed in the DMPS-treated rabbits. The above-mentioned biochemical changes should be taken into account in studies of possible chelating and radical scavenging effects of DMPS in various pathological conditions.

The effects of subchronical exposure to SO2 on biochemical and hematological parameters in guinea pigs.

The effects of subchronical exposure to SO2 (400ppm, 3 hours daily, 28 days) on biochemical and hematological parameters were investigated in guinea pigs. Mostly no significant changes in the values of biochemical parameters and no significant changes in hematological parameters were found. The levels of investigated ions (K+, Na+, Cl-, Ca++, Mg++ and phosphates), proteins (albumines, globulines, total proteins), enzymes (LD, ALT, AST, CK) and other biochemical parameters (urea, creatinine, bilirubin) were not significantly different between groups, with the exception of a significantly higher ALP concentration in the exposed group as compared with controls (2.17 mukat and 1.85 mukat, respectively. It can be concluded that a subchronical exposure to sulphur dioxide mostly did not induce any definite changes in biochemical and hematological parameters in guinea pigs.