Effects of prolonged caffeine consumption on cardiac contractile function in rats

The purpose of the study was to explore effects of prolonged caffeine admin istration on the contractile function and myocardial energy metabolites of the isolated rat heart. Caffeine treatment for 1 week (10 mg/kg, i.p., twic e a day) was followed by unchanged pump function of the isolated heart, but reduced maximal left ventricular (LV) systolic pressure by 14% (p < 0.05). Caffeine consumption during 8-9 weeks (0.1% water solution) was also follo wed by unchanged maximal pump function but increased maximal double product (LV developed pressure multiplied by heart rate) by 23% (p < 0.05). The he arts of caffeine-consumed rats also maintained a higher level of the pump f unction at a high rate of atrial electrostimulation. The myocardial content of adenosine triphosphate (ATP), creatine phosphate, as well as creatine w as slightly but insignificantly increased after caffeine consumption. Resul ts show that in the course of prolonged caffeine treatment, the maximal myo cardial contractile function first decreases and then increases, showing ad aptation of the heart.