Abstract: AIM: To observe the effects of mannitol in isolated rat hearts. METHODS: The langendorff system was used to evaluate the function of rat hearts treated with mannitol (20 mmol/L, 40 mmol/L and 60 mmol/L respectively). Following a stabilization period of 30 min, the isolated hearts were subjected to continuous perfusion for a further 60 min with vehicle or increasing concentration of mannitol. Heart functional indexes including left ventricular develop pressure (LVDP), rate-pressure product (RPP), maximal rate of pressure increased (+dpp/dt_max), maximal rate of pressure decreased (-dp/dt_max), left ventricular end diastolic pressure (LVEDP) and coronary flow were recorded.RESULTS: LVDP,+dp/dt_max and RPP were increased significantly in hearts perfused with 20 mmol/L mannitol in a time dependent manner. However, when the hearts perfused with 40 mmol/L or 60 mmol/L mannitol, time used for reaching the maximum LVDP,+dp/dt_max and RPP by 40 mmol/L and 60 mmol/L mannitol was shorter in hearts treated with 20 mmol/L mannitol. More, the results demonstrated that heart treated with 60 mmol/L mannitol could significantly increase the LVDEP and decrease the -dp/dt_max. CONCLUSION: Mannitol could affect left ventricular contraction function in a time and concentration dependent manner. Ventricular diastolic function was weakened by perfusing the high concentration of mannitol.

Key words: Mannitol, Isolated heart, Perfusion