The Role of Nitric Oxide and Prostaglandins in the Effect of Adenosine on Contractility, Heart Rate and Coronary Blood Flow in Guinea Pig Isolated Heart

It is a well-established fact that adenosine and its receptor subtypes (A 1 and A ) are involved in changes of contractility, heart rate and coronary blood flow (CBF) under different circumstances. This study was conducted to evaluate the role of nitric oxide and prostaglandins in development of these changes. For this purpose, Nitro-L-Arginine methyl ester (L-NAME), and indomethacin as inhibitors of nitric oxide and prostaglandins synthesis were used respectively. In this respect, guinea pig isolated hearts were randomly divided into control (receiving adenosine) and groups II and III which received L-NAME (100 µM) and indomethacin (50 nM) before adenosine application, respectively, using isolated heart setup. The results showed that adenosine increased CBF and decreased heart rate and contractility in control group. In the presence of L-NAME, adenosine was less effective in enhancing the CBF and decreasing cardiac contractility. Furthermore, no significant change was observed in the presence of indomethacin (regarding all of parameters). It can be concluded that nitric oxide (and not prostaglandins) is essential for the effect of adenosine on CBF and cardiac contractility. Iran. Biomed. J. 9 (4): 177-180, 2005 2