RESUMO
In the West Indies a wide variety of local plants are used in the treatment of several illnesses (folk medicine). The aqueous extract of anacardium occidentale is used in Jamaica to treat diabetes mellitus. It has reported that intravenous administration of a tincture or the bark lowered the blood sugar level for several hours; however our preliminary experiments in this study revealed no antidiabetic property. On the other hand the aqueous extract of the bark possesses cardiac antiarrhythmic properties. The antiarrhythmic agent was isolated and shown to be identical with myoinositol which constitutes about 25 percent of the extract material. The cardiovascular studies were conducted on adult mongrel dogs and adult cats of either sex. Only in the dog was left ventricular contractile force measured. Cardiac arrhythmias were induced by the infusion of adrenaline at 3 ug/kg/min and were easily maintained. This does caused multiple atrial or ventricular extrasystoles, or ventricular tachycardia within two minutes of starting the infusion. Myoinositol was injected intravenously before and during the adrenaline infusion in doses of 1-2 mg/kg. In cases where myoinositol was given before adrenaline, five to ten minutes were allowed before the infusion of adrenaline was started. The results indicated that myoinositol at this dose level had no significant effect upon pulsatile blood pressure. E.C.G. (lead 11) heart rate and contractile force in the normal animal. After the above dose of myoinositol was given the animal could withstand infusions of adrenaline as high as 6 ug/kg/min for up to 60 minutes without arrhythmias. Myoinositol does not interfere with the bet-adrenergic effect of adrenaline on the heart, hence this antiarrhythmic effect might not be mediated through a beta-adrenergic mechanism. On the other hand, since the compound has no local anaesthetic effect and does not depress the myocardium at the dosage that protects against adrenaline induce arrhythias, this effect cannot be due to a myocardial action. It is well known that myoinositol is found in various tissues of the mammalian body with the highest concentration in cardiac muscle (1.6 percent) but its exact physiolodical role is uncertain. Further work is being carried out using other types of arrhythmias with a view to elucidate the mechanism of this antiarrhythmic action (AU)
