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[Mechanism of the cardiotoxic action of No-Spa]
Abstract:
Tests set up in vivo on rats and with an isolated spontaneously contracting atrium of the cat brought evidence that nospanum produces an adverse chronotropic action, caused by a direct effect on the cardiac pacemaker. In the rat's myocardium the drug raised the pyruvate level, increased the lactate-dehydrogenase activity and depressed that of glucose-6-phosphate-dehydrogenase. As established by differential spectrophotometry the reduced forms of pyridine-nucleotides (NAD'N, NADP'N) tend to change the nospanum spectrum. An addition of potassium chloride to an isolated atrium at the peak of the adverse chronotropic action of nospanum or an introduction of nospanum together with NAD'N abolished the cardiotropic effect of the drug. The mechanism of the cardiotoxic action of nospanum is discussed.
Insights
Nospanum negatively impacts heart rate by directly affecting the cardiac pacemaker. Its cardiotoxic effects in rats involve altered pyruvate and dehydrogenase levels, which can be counteracted by potassium chloride or NAD'N.
Area of Science:
- Cardiology
- Pharmacology
- Biochemistry
Background:
- Nospanum's cardiac effects require further elucidation.
- Understanding drug-induced cardiotoxicity is crucial for patient safety.
Purpose of the Study:
- To investigate the adverse chronotropic action of nospanum.
- To explore the biochemical mechanisms underlying nospanum's cardiotoxicity.
Main Methods:
- In vivo studies on rats and in vitro experiments on isolated cat atria.
- Measurement of myocardial pyruvate and lactate-dehydrogenase (LDH) and glucose-6-phosphate-dehydrogenase (G6PD) activities.
- Differential spectrophotometry to analyze pyridine-nucleotide changes.
Main Results:
- Nospanum demonstrated an adverse chronotropic effect, directly impacting the cardiac pacemaker.
- In rat myocardium, nospanum increased pyruvate and LDH activity while decreasing G6PD activity.
- Changes in reduced pyridine-nucleotides (NAD'N, NADP'N) were observed.
- Potassium chloride and NAD'N mitigated nospanum's cardiotropic effects.
Conclusions:
- Nospanum exerts a direct negative chronotropic effect on the heart.
- The drug interferes with myocardial energy metabolism, affecting key enzymes and pyridine-nucleotides.
- Intervention with potassium or NAD'N suggests a role for these in counteracting nospanum's cardiotoxicity.