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Free radical scavengers fail to increase the protective effects of ranolazine in isolated wotting rat nearts after ischemia and reperfusion
1982) in which vitamin E as an antioxidant and zinc as a medwau~e stabiiig omyopathy. On the other hand, 2 *&es pretreatments with Prop (100 mg/kg/‘day, e IR-induced cardiac hypertrophy and histological changes plasma and ventricles. 1988) and SOD, P’ITU, alloputinol and glutathione were antioxidative effect of Prop as well as bek-blocking effect may participate in its strong prophylactic IPrGmluced cardiac injury. The above results suggest that the autooxidation of IF? partially plays a role cardiac injury and the excessive stimulation of IPr as well.
P.O., 1974,J. Mol. Cell.Cardiol.6, 49-60. Physiol.Phannacol.60,1390-1397. 988,Circ.Res.63,262-266.
azine in isol
F-don, Depamnent of Phamwdogv,
P., Chaylat, C. and Armstrong, J.M. Recherche Syntex France, F-91310, Leuville-sur-Orge, France
It has been suggested that the release and activity of free radicals of oxygen contributes to the production of cardiac ventricular arrhythmias induced by ischemia and reperfusion and that removal of such radicals should have a beneficial effect (Woodward and Manning, 1987). We have looked for an interaction between ranolazine (1 CM), a novel anti-ischemic agent active in models of cardiac ischemia (Ferrandon et al., 1988), and three radical scavengers (Super Oxyde-Dismutase, SOD-30 U/ml; Catalase, C-100 U/ml; Mannitol, M-20 n&I) used at concentrations previously shown to protect hearts from reperfusion injury (Woodward and Zakaria, 1985). Working rats hearts were perfused with Krebs’s solution via the pulmonary veins and ventricular ischemia and mperf&ion effected by first ligating the left coronary srtc-’ &, and ‘ihen cutting the ligature 15 min later. Agents were added to the perfusion fluid 10 min prior to coronary ligation. Measurements were made of the duration of evoked fibrillation (ruin) and the aortic flow (ml/mm) of hearts surviving reperfusion. The results (means and SEM) are shown in the table and the significance of the difference between means ( * from controls; # from ranohtzine) assessed using either 95% estimated odds ratio; p = 0.09 for survival or unpaired Student’s t-test; p < 0,OSfor aortic flow. The mean aortic flow before ischemia was 51,7 f 0,6 ml.min-* for all groups. II
Controls S.O.D.30U/ml Catahw loo u/ml MamitolO.01M c + MaMitol S.O.D.+ C + M Ranolazine Ranolazine + S.O.D. Ranohzine+ C
8 9 8 7 7 7 16 9 7
Fib. duration
survival
Aorticflow
11.7f4.7 11.6f 1.6 7.1f 2.4 12.8*2.1 11.5f2.3 117f 1.9 4.8f1.7 4.5f 2.5 8.5f 2.9 .._
25 33 50 0 28 14 75 * 78 * 43
12.8f4.5 P3.0f9.5 11.6f2.3 10.4f 9.2 17.2 25.8f3.3 + 18.5f 4.4 8.1fS.l #
None of the radical scavengers protected hearts from reperfusion when used either alone or in combination. Furthermore, the protective effect of rauolazine was not increased when it was administrated together with either SOD or C.
329
The results suggest that free radicals of oxygen do not contribute to reperfusion injury in the present conditions and that ranolazine’s protective effects are mediated by mechanisms that are not revealed here.
References Ferrandon, P., Pascal, J.C. and Armstrong,J.M., 1988,Br. J. Pharm. 93,247P. Woodward,II and Zakaria,N.M., 1985,J. Mol. Cell.Cardiol.17,485. Woodward, B. and Manning, AS., 1987, in: Life-ThreateningArrhythmias during Ischemia and infarction. Eds D. Hearse, Manningand M. Janse. Raven Press. (New York) p. 115.
A.
El
P.mo.141
xyl radical scavenging activity o
e Ca++
Constantin, M., Poignet, C. and Massingham, R. Department of Pharmacology, RL-@ERM, Route de Marsat. 63203 Riom, France
Oxygen free radical species have been implicated as important agents in myocardial ischemia, particulary in reperfusion injury, arrhythmias and in the stunned myocardium phenomenon. It is believed that hydroxyl radicals ( OOH) induce cell damage by the peroxidation of membrane phospholipids which thereby alters cellular integrity. In this study the OOH scavenging abilities of b@dil, diltiazem and verapamil have been examined. Compounds were tested in vitro on deoxyribose degradation by o OH generated with a Fe+++-ascorbate-H,O, system and in vivo, using alloxan-induced diabetis in mice. Current opinion holds that mainly OOH radicals are involved in the cytotoxic action of alloxan at the pancreatic /l cells in this species. In the in vitro model, the concentrations of bepridil, diltiazem and verapamil required to inhibit deoxyribose degradation by OOH radicals by 50% were 0.054, 0.108 and 0.052 PM respectively for the 3 compounds. In the in vivo model, hyperglycaemia was induced in groups of mice by the injection of 60 mg/kg i-v. alloxan and test drugs were administered intraperitonrtiy, at various doses, 30 min before the alloxan. Plasma glucose levels were measured 3 days after alloxan administration. Results are shown in Table 1. Table 1 Inhibition of alloxan-induced
increases in plasma glucose levels in mice.
Dose mmole/kg
% inhibition of alloxan-induced Beplidil
Diltiazem
hyperglycaemic Verapamil
0.038 0.075
nt 30 +*
nt 38 +
0.150
69 +O
66 *+
69 ** 83 ** (60% mortality) 83 ** (63% mortality)
-
nt = not tested ** P
In conclusion, these results have demonstrated that in the in vitro model, bepridil had equivalent activity to verapamil and was twice as active as diltiazem as an “OH radical scavenger. In the in vivo model, bepridil was equipotent to diltiazem and some 4 times less potent than verapam?.. However if account is taken of the doses of these drugs required to elicit pharmacological effects in vivo (bepridil: 25 mg/kg i.v., verapamil and diltiazem: O-l-O,3 mg/kg i.v.), then of the 3 compounds, only with bepridil could ‘OH radical scavenging properties possibly be implicated in the therapeutic action of the drug.
P.O., 1974,J. Mol. Cell.Cardiol.6, 49-60. Physiol.Phannacol.60,1390-1397. 988,Circ.Res.63,262-266.
azine in isol
F-don, Depamnent of Phamwdogv,
P., Chaylat, C. and Armstrong, J.M. Recherche Syntex France, F-91310, Leuville-sur-Orge, France
It has been suggested that the release and activity of free radicals of oxygen contributes to the production of cardiac ventricular arrhythmias induced by ischemia and reperfusion and that removal of such radicals should have a beneficial effect (Woodward and Manning, 1987). We have looked for an interaction between ranolazine (1 CM), a novel anti-ischemic agent active in models of cardiac ischemia (Ferrandon et al., 1988), and three radical scavengers (Super Oxyde-Dismutase, SOD-30 U/ml; Catalase, C-100 U/ml; Mannitol, M-20 n&I) used at concentrations previously shown to protect hearts from reperfusion injury (Woodward and Zakaria, 1985). Working rats hearts were perfused with Krebs’s solution via the pulmonary veins and ventricular ischemia and mperf&ion effected by first ligating the left coronary srtc-’ &, and ‘ihen cutting the ligature 15 min later. Agents were added to the perfusion fluid 10 min prior to coronary ligation. Measurements were made of the duration of evoked fibrillation (ruin) and the aortic flow (ml/mm) of hearts surviving reperfusion. The results (means and SEM) are shown in the table and the significance of the difference between means ( * from controls; # from ranohtzine) assessed using either 95% estimated odds ratio; p = 0.09 for survival or unpaired Student’s t-test; p < 0,OSfor aortic flow. The mean aortic flow before ischemia was 51,7 f 0,6 ml.min-* for all groups. II
Controls S.O.D.30U/ml Catahw loo u/ml MamitolO.01M c + MaMitol S.O.D.+ C + M Ranolazine Ranolazine + S.O.D. Ranohzine+ C
8 9 8 7 7 7 16 9 7
Fib. duration
survival
Aorticflow
11.7f4.7 11.6f 1.6 7.1f 2.4 12.8*2.1 11.5f2.3 117f 1.9 4.8f1.7 4.5f 2.5 8.5f 2.9 .._
25 33 50 0 28 14 75 * 78 * 43
12.8f4.5 P3.0f9.5 11.6f2.3 10.4f 9.2 17.2 25.8f3.3 + 18.5f 4.4 8.1fS.l #
None of the radical scavengers protected hearts from reperfusion when used either alone or in combination. Furthermore, the protective effect of rauolazine was not increased when it was administrated together with either SOD or C.
329
The results suggest that free radicals of oxygen do not contribute to reperfusion injury in the present conditions and that ranolazine’s protective effects are mediated by mechanisms that are not revealed here.
References Ferrandon, P., Pascal, J.C. and Armstrong,J.M., 1988,Br. J. Pharm. 93,247P. Woodward,II and Zakaria,N.M., 1985,J. Mol. Cell.Cardiol.17,485. Woodward, B. and Manning, AS., 1987, in: Life-ThreateningArrhythmias during Ischemia and infarction. Eds D. Hearse, Manningand M. Janse. Raven Press. (New York) p. 115.
A.
El
P.mo.141
xyl radical scavenging activity o
e Ca++
Constantin, M., Poignet, C. and Massingham, R. Department of Pharmacology, RL-@ERM, Route de Marsat. 63203 Riom, France
Oxygen free radical species have been implicated as important agents in myocardial ischemia, particulary in reperfusion injury, arrhythmias and in the stunned myocardium phenomenon. It is believed that hydroxyl radicals ( OOH) induce cell damage by the peroxidation of membrane phospholipids which thereby alters cellular integrity. In this study the OOH scavenging abilities of b@dil, diltiazem and verapamil have been examined. Compounds were tested in vitro on deoxyribose degradation by o OH generated with a Fe+++-ascorbate-H,O, system and in vivo, using alloxan-induced diabetis in mice. Current opinion holds that mainly OOH radicals are involved in the cytotoxic action of alloxan at the pancreatic /l cells in this species. In the in vitro model, the concentrations of bepridil, diltiazem and verapamil required to inhibit deoxyribose degradation by OOH radicals by 50% were 0.054, 0.108 and 0.052 PM respectively for the 3 compounds. In the in vivo model, hyperglycaemia was induced in groups of mice by the injection of 60 mg/kg i-v. alloxan and test drugs were administered intraperitonrtiy, at various doses, 30 min before the alloxan. Plasma glucose levels were measured 3 days after alloxan administration. Results are shown in Table 1. Table 1 Inhibition of alloxan-induced
increases in plasma glucose levels in mice.
Dose mmole/kg
% inhibition of alloxan-induced Beplidil
Diltiazem
hyperglycaemic Verapamil
0.038 0.075
nt 30 +*
nt 38 +
0.150
69 +O
66 *+
69 ** 83 ** (60% mortality) 83 ** (63% mortality)
-
nt = not tested ** P
In conclusion, these results have demonstrated that in the in vitro model, bepridil had equivalent activity to verapamil and was twice as active as diltiazem as an “OH radical scavenger. In the in vivo model, bepridil was equipotent to diltiazem and some 4 times less potent than verapam?.. However if account is taken of the doses of these drugs required to elicit pharmacological effects in vivo (bepridil: 25 mg/kg i.v., verapamil and diltiazem: O-l-O,3 mg/kg i.v.), then of the 3 compounds, only with bepridil could ‘OH radical scavenging properties possibly be implicated in the therapeutic action of the drug.