Increased basal and adenosine‐mediated coronary flow in ex vivo hearts from type I diabetic mice (1051.16)

Diabetes is known to cause morphological and functional changes in the cardiovascular system, resulting in abnormal responses to various stimuli such as adenosine. Our aim was to examine the functional changes in coronary flow (CF) to adenosine receptor (AR) agonists resulting from type I diabetes. Diabetes was induced in mice using streptozotocin (STZ, 10mg/Kg; 8 weeks) and concentration response curves to the non-selective AR agonist NECA and to the A2A AR selective agonist (CGS-21680; CGS) were performed in isolated perfused hearts from STZ and vehicle (C) group. Diabetes resulted in a decrease in heart weight (0.093g ± 0.002 in STZ vs. 0.117g ± 0.004 in C; p<0.05), an increase in blood glucose level (510.8mg/dL ± 22.2 in STZ vs. 140.9mg/dL ± 9.4 in C; p<0.05) and an increase in the basal coronary flow (21.6 ± 1.5 in STZ vs. 16.1 ± 0.6 in C; p<0.05). Both NECA and CGS induced a concentration-dependent increase in CF (ml.min-1.mg-1) which was significantly increased in STZ compared to C (NECA: Emax 39.8 ± 1.8 in STZ vs. 28.2 ± 0.7 in C; p<0.05) (CGS; Emax 38.8 ± 1 in STZ vs. 28.3 ± 1.8 in C; p<0.05). No significant differences were observed between the groups for changes in both heart rate and left ventricular diastolic pressure to both agonists. Our data suggest that STZ-induced diabetes resulted in an increase in basal CF as well as increased vasodilatory response to adenosine agonists, probably by upregulating A2A receptor signaling.