- Distribution and functional characterization of equilibrative nucleoside transporter-4, a novel cardiac adenosine transporter activated at acidic pH. Barnes, K., Dobrzynski, H., Foppolo, S., Beal, P.R., Ismat, F., Scullion, E.R., Sun, L., Tellez, J., Ritzel, M.W., Claycomb, W.C., Cass, C.E., Young, J.D., Billeter-Clark, R., Boyett, M.R., Baldwin, S.A. Circ. Res. (2006)