Effect of adenosine A₂-receptor activation and direct stimulation of adenylyl cyclase with forskolin on P-5′-N activity. RBC cells from day-11 chick embryos were incubated for 16 hours with either 10 μmol/L CPCA or 100 μmol/L forskolin, and P-5′-N activity was determined for control and stimulated samples at the end of the incubation period. Data are the mean values and SD from five experiments. The asterisk indicates statistically significant difference tested by the Student'st-test for paired samples (***P < .001).