Alterations of the cardiac contractile function of rats after prolonged caffeine consumption

Aim. To study contractile function and energy metabolism of isolated hearts of rats after 1 week and 8-9 weeks of treatment with caffeine. Results. Ca ffeine injection (10 mg/kg i.v.) into conscious rats resulted in transient decreases of left ventricular (LV) systolic pressure as well as its first d erivative, dP/dt, and increases of heart rate and LV minimal diastolic pres sure. One week of caffeine treatment (10 mg/kg i.p. twice a day) did not ch ange pump function compared to control. However at maximal resistance to el ection induced by aortic flow clamping maximal LV systolic pressure and mea n aortic pressure in aortic chamber decreased by 14 and 12%, respectively. Caffeine consumption for 8-9 weeks (0,1% solution) also did not change maxi mal pump function but, at maximal resistance to ejection, maximal intensity of contractile function (double product of LV developed pressure and heart rate) increased by 23% (p<0,05), Although maximal cardiac work after caffe ine consumption did not significantly differ from the control value, an inc reased by 44% aortic output was combined with significantly lower LV minima l diastolic pressure suggesting improved LV filling, Moreover, the hearts o f caffeine-treated rats were able to maintain higher level of the pump func tion at high rates of atrial pacing. The myocardial content of ATP, creatin e phosphate as well as creatine remained unchanged after caffeine consumpti on. Cross correlation analysis of energetic and functional data revealed th at total pool of adenine nucleotides was most important for cardiac contrac tile function (correlation coefficients 0,64-0,74). Conclusion. Caffeine tr eatment resulted in initial (after 1 week) decrease of maximal values of th e pressure development followed by their subsequent: increase after 8-9 wee ks. This change was associated with improvement of the cardiac pump functio n at high stimulation frequencies. Thus prolonged exposure to caffeine poss ibly resulted in alterations of cardiomyocytes that were opposite to those caused by acute caffeine action.