Adenosine transporters in chromaffin cells

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Abstract
Chromaffin cells from bovine adrenal medulla are a useful model to approach adenosine transport and metabolism in neural cells. Dipyridamol has been shown to be an adenosine transport inhibitor with high affinity. To quantify the adenosine transporters a labelled dipyridamol analogue, [14C]dipyridamol acetate, was synthesized. This compound had a K i = 5.3 ± 0.43 nM according to the Dixon method, and 4.58 ± 0.46 nM when the receptor number molarity was taken into account showing, like dipyridamol, a non‐competitive mechanism. The high‐affinity receptors present in chromaffin cells showed a K d = 6.8 ± 0.8 nM and the receptor number was 630000 ± 40000 per cell.