Elevated interstitial adenosine concentrations do not activate the muscle reflex

The purpose of the present study was to examine the effects of adenosine pe rfusion of the isolated triceps surae muscle group in the decerebrate cat o n interstitial adenosine concentrations as well as heart rate and blood pre ssure responses. In six male cats (6.0 +/- 0.21 kg), the triceps surae musc le group of both legs was perfused with an artificial blood solution contai ning no additives (control) and then with blood containing 20 mM or 100 muM adenosine for 10 min. An intact muscle reflex was confirmed by bolus injec tions of 50 mM phosphate and/or saturated KCl administered into the triceps surae muscle via the cannulated popliteal artery before and after adenosin e blood perfusion. Microdialysis of the triceps surae muscle group during m uscle perfusion revealed that interstitial adenosine was elevated (P< 0.05) from 0.9 +/- 0.3 <mu>M during control blood perfusion to 2,421 +/- 547 muM during 20 mM adenosine perfusion. In addition, interstitial adenosine leve ls were increased (P< 0.05) from 1.1 +/- 0.3 <mu>M during control blood per fusion to 4.1 +/- 1.2 muM during perfusion with 100 muM adenosine. Despite the large increases in interstitial adenosine levels, perfusion of the tric eps surae muscle group with the two blood adenosine solutions resulted in n o significant increases in heart rate or blood pressure. These data strongl y suggest that elevated interstitial adenosine concentrations do not play a role in activating the muscle reflex and confirm our previous in vivo huma n findings.