Objective: 

The aim of this study was to compare the hemodynamic effects of atrial natriuretic peptide (ANP) in ischemia followed by reperfusion in exercised rat heart with the non-exercised one.

Methods: 

Male Sprague-Dawley rats were divided into exercise (E1, E2, E3, E4, E5) and non-exercise (NE1, NE2, NE3, NE4, NE5, NE6) groups (n=6 each). E groups were exposed to running protocol for 5 days. Global ischemia (35 minutes) and 30-minute-reperfusion were applied in E1 and NE1 groups. ANP (0.1 mM/L) was also administered before ischemia in E2 and NE2 groups. Isatin (0.1-10-100 mM/L), which is known as ANP receptor blocker, was administered before ANP in E3, E4, E5 and NE3, NE4, NE5 and NE6 (without ANP) groups. Left ventricular developed pressure (DP) and the maximum-minimum rates of change in left ventricular pressure (dp/dtmax, dp/dtmin) were recorded during the experiments.

Results: 

Significantly decreased DP values were shown in E1 (103±13.0 versus 15.4±14.9 mmHg) and NE1 (110.8±12.2 versus 63.4±28.7 mmHg) groups at the 1 sec of reperfusion (p<0.01 and p<0.05). Hovewer no significant decrease in DP (80.3±7.9 versus 54.5±19.7 mmHg), +dp/dt (1408.0±330.3 mmHg/s versus 394.5±278.4 mmHg/s) and -dp/dt (-1725.0±181.7 mmHg/s versus -833.6±193.8 mmHg/s) values was observed in E2 group at the 1 sec of reperfusion. Infusion of different doses of isatin did not significantly change hemodynamic values in groups.

Conclusion: This study indicated that deleterius contractile force occur in reperfusion period following short term treadmill running in the left ventricle. Administration of ANP before ischemia may improve decreased contractile forces in reperfusion period in exercised rat heart.