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In Vivo Quantification of Myocardial Dihydropyridine Binding Sites: A PET Study in Dogs

¹ Department of Medical Research, Direction of Life Sciences, Service Hospitalier Frédéric Joliot, French Atomic Agency, Orsay, France
² Institut de Recherche Servier, Suresnes, France

View larger version (17K): [in a new window]   FIGURE 1. Four-compartment ligand-receptor model used in analysis of S12968 time-concentration curves obtained with PET. All transfer probabilities of ligand between compartments are linear, except binding probability, which depends on local association rate constant (kon), local free ligand concentration (M*f(t)/VR), and local concentration of receptor sites (Bmax - M*b(t)). PET experimental data correspond to sum of labeled ligand in 3 tissue compartments and in fraction FV of blood concentration. M*ns(t) = nonspecifically bound radioligand.

View larger version (13K): [in a new window]   FIGURE 2. PET left ventricular time-activity curve after injection of 9.9-nmol dose of 11C-S12968, followed 20 min later by injection of 8.8 nmol, followed 20 min later by injection of 10.1 nmol. Time-activity curve is characterized by low noise contribution. Quality of fit of experimental data to 3-compartment mathematic model is satisfactory. DATA = data from experiment 3; MODEL = 3-compartment mathematic model.

View larger version (9K): [in a new window]   FIGURE 3. Relationship between injected mass of S12968 and left ventricular uptake, estimated by K1. Correlation was clearly linear.

View larger version (10K): [in a new window]   FIGURE 4. Relationship between injected mass of S12968 and left ventricular washout, estimated by k2. Correlation was clearly linear.

View larger version (11K): [in a new window]   FIGURE 5. Mean (experiments 3–5) and SD of unchanged 11C-S12968 in plasma, as function of time. Shape of curve remained coarsely unchanged after each of the 3 injections.

View larger version (17K): [in a new window]   FIGURE 6. Computer simulation of S12968 kinetics during multiinjection experiment (PET data from experiment 3, as in Fig. 2). Figure shows S12968 concentration in all compartments simulated using model parameters given in Table 3: specifically bound ligand concentration and free ligand. Solid line is simulation of PET-measured S12968 concentration.