Acetaldehyde, a metabolite of ethanol has not only been implicated as a contributory factor that cause alcoholic cardiomyopathies but also has been shown to have signifi-cant cardiovascular effects. The suggestion has also been made that acetaldehyde has more pronounced effect on the cardiovascular system than ethanol. Several epidemiological studies have demonstrated that alcoholism is associated with heavy smoking thereby increasing the risk of developing various ailments. Also nicotine has been known to influence the cardiovascular functions profoundly.
In the present study, changes in the intracellular action potential were investigated ink the sinoatrial node cells of the rabbit heart for 45 minutes following superfusion with Tyrode solutions containing acetaldehyde and/or nicotine.
Superfusion of the sinus node cells with acetaldehyde (0.01%-0.1%) resulted in a concentration-dependent reduction of action potential amplitude.(APA). At´ the high dosage level (0.1%) changes in APA peaked at 10 minutes and APA was restored to the controll level in 45 minutes after onset of superfusion. And Vmax (maximum rate of depolarization) of the sinus node cell was also decreased by acetaldehyde. The rate of spontaneous firing (RSF) of the sinus node cells was markedly decreased by acetaldehyde (0.05%-0.1%), but the action potential duration manifested as APD60 (time to 60% repolarization) was not altered.
On the other hand, nicotine (0.05%) increased APA, prolonged APD6Q and significantly decreased RSF of the sinus node cells. The maximal changes in APA and APD6o were produced at 10 minutes while that in RSF at 7 minutes after onset of superfusion.
Following simultaneous superfusion with acetaldehyde and nicotine, APA and RSF of the sinus node cells decreased prominently whereas a transient, small but signifi-cant prolongation of APD6o was followed by a transient shortening.
When the sinus node cells were superfused with acetaldehyde and nicotine simultaneously, it appeared that effects of two drugs on APA were exerted in ad-ditive fashion while that of nicotine on RSF was partially antagonized by acetaldehyde.
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