Fig. 5. Influence of an adenosine receptor antagonist and agonist on adenosine action. COX activities were determined in isolated hepatocytes after 48 or 72 h of incubation and normalized to the mean of the control group. Cells were treated with the adenosine receptor antagonist 8-PT combined with adenosine (ado) or with the adenosine agonist NECA instead of adenosine and are compared to their analogous control and adenosine-treated groups. All reagents were supplied at a concentration of 100 nmol ml^–1. Cells were prepared from warm-acclimated Z. viviparus and incubated at 11°C. ^*Significant difference from control. Values are means ± s.e.m. (N=4–6).