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Kinetic analysis of the transport protein (both influx and efflux), usually performed with radiolabelled nucleosides such as adenosine and uridine, has provided a wealth of information regarding the various kinetic and equilibrium parameters (1).

The RP-HPLC determination of drug lipophilicity was evaluated for its potency as a substitute for the determination of log P(Oct-W) values. The relation of log k(w) to log P(app) (= log P(Oct-W) at pH 7.4) is linear for a testset including protonable nitrogen bases. The method is reproducible on different columns (with the same brand and type of the stationary phases) and needs no recalibration then. Three series of substituted benzene homologues (one hydrogen bond acceptor and two weak donor groups) demonstrate structure-retention effects.

The influence of nifedipine (20 nM) and mioflazine (300 nM), i.e. concentrations inducing a 60–70% recovery of cardiac function during reperfusion of globally ischaemic guinea-pig working beans, on the mitochondrial calcium content was investigated in normoxic, globally ischaemic and reperfused globally ischaemic guinea-pig working hearts. Mitochondrial calcium was determined electronmicroscopically with the oxalate-pyroantimonate method. In normoxic hearts both nifedipine and mioflazine reduced the mitochondrial calcium content. Global ischaemia for 45 min and subsequent reperfusion for 25 min resulted in a pronounced mitochondrial calcium overload and damage to the cellular structure. In ischaemic and in reperfusion hearts the drugs maintained mitochondrial calcium at pre-ischaemic levels and decreased the damage to the cellular structure.

The transport of nucleosides and analogues across the plasma membrane of animal cells is mediated by nucleoside-specific transport proteins, by means of facilitated diffusion. Development of highly potent tritiated transport inhibitors allowed ligand binding studies, performed at various tissues. [3H]Nitrobenzylthioinosine ([3HINBI) and [3H]dipyridamole are used in this respect, yielding a wealth of information about the molecular characteristics of these proteins (1,2).