Intracellular adenosine formation and its carrier-mediated release in cultured embryonic chick heart cells

Adenosine formation and release was examined in 48 hr old primary cultures of chick ventricular myocytes. Dilazep greater than hexobendine greater than dipyridamole inhibit incorporation of adenosine into chick embryonic heart cellular nucleotides in a concentration dependent manner. A combination of 30 mM 2-deoxyglucose and 2 micrograms of oligomycin/ml reduces the ATP content of the cells by 71% in 10 min. This change is accompanied by an increase in total adenosine concentration of 3.4 nmoles/10(7) cells in 10 min. Although the ATP concentration is not altered during hypoxia (95%N2/5%CO2), adenosine concentration increases by 0.52 nmoles/10(7) cells in 30 min. When nucleoside incorporation is inhibited by 85-90% by dipyridamole, dilazep or hexobendine, efflux of adenosine decreases by 70-90%, and 60-90% of the newly formed adenosine is trapped inside the cells compared to 10% in the absence of the transport inhibitors. alpha, beta -Methylene ADP inhibits the ecto 5'-nucleotidase activity by 91 +/- 6% but does not inhibit adenosine formation or alter its distribution between cells and medium, thus ruling out the involvement of this enzyme in adenosine formation. We conclude that adenosine is formed intracellularly during 2-deoxyglucose and oligomycin-induced ATP degradation and during hypoxia and that the nucleoside is released via the symmetric nucleoside transporter.