[Effects of levocarnitine chloride (LC-80) on the cardiovascular system].
The cardiovascular effects of levocarnitine chloride (LC-80) were investigated in in vitro and in vivo experiments, and the following results were obtained: (1) In isolated rabbit cardiac muscle preparations, LC-80 at the high concentration of 10(-2) M had little influence on the atrial rate of spontaneously beating right atria, while it caused a gradual increase in the contractile tension of both spontaneously beating right atria and electrically driven papillary muscle that reached a maximum level after 10 min of administration and lasted for 20-30 min. However, the LC-80-induced positive inotropic effect may be negligible in whole animal experiments or clinical trials, since it was elicited only after the administration of LC-80 in an extremely large dose. Furthermore, LC-80 in a high concentration (10(-2) M) had no influence on the isoproterenol-induced positive inotropic effect in electrically driven papillary muscles. (2) LC-80 in high concentrations of 10(-3)-10(-2) M did not affect the high K+-induced contraction in isolated canine left circumflex coronary artery and saphenous vein. (3) In anesthetized dogs, intraarterial injection of LC-80 in high doses of up to 10 mg did not change the blood flow of coronary, femoral, renal, mesenteric or vertebral arteries and on the adenosine-induced vasodilator action. (4) In anesthetized dogs, intravenous injection of LC-80 in doses of 100-300 mg/kg did not modify the blood pressure responses induced by norepinephrine, acetylcholine, carotid occlusion and vagal stimulation. These results suggest that the cardiovascular effects of LC-80 are extremely mild or negligible. Therefore, LC-80 may be a drug having a new pharmacological feature in its mechanism which enables it to exert a beneficial effect in the treatment of ischemic heart disease, being different from the commonly used antianginal drugs.