Flow cytometric studies of nucleoside transport regulation in single chromaffin cells

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Abstract
The present paper reveals that a fluorescent derivative of nitrobenzylthioinosine, 5‐(SAENTA‐x8)‐fluorescein, is a highly specific inhibitor of the neural NBTI‐sensitive nucleoside transporter. 5‐(SAENTA‐x8)‐fluorescein inhibited adenosine transport and [3H]NBTI binding with a K i of 4 nM in cultured chromaffin cells. Flow cytometry demonstrated that 5‐(SAENTA‐x8)‐fluorescein specifically interacted with the NBTI‐sensitive nucleoside transporters with high affinity (K D=6 nM). Activation of protein kinases A and C with forskolin or nicotinic receptor agonists, respectively, resulted in 50% inhibition of the fluorescence bound to the cells. Flow cytometry will allow studying nucleoside transport in single cells from heterogeneous neural cell populations.