Tracer washout rate

Several F-labeled fatty acid derivatives have been successfully prepared and evaluated as potential FAO assessing tracers [19-24]. Methyl-branched-chain (w- F-fluorofatty acids, such as 3-methyl-(3-MFHA) and 5-methyl-17-[ F]fluoro-heptadecanoic acid (5-MFHA), have been reported [23]. In a comparative study, it was found that rw-[ F]fluoropalmitic acid (FPA) exhibits the highest myocardial uptake, followed by 5-MFHA and 3-MFHA. FPA possesses the fastest myocardial washout rate, and 3-MFHA the slowest. In lipid analysis studies, 5-MFHA... 

The rate at which solute is washed out of the capillary-tissue unit depends on the number of barriers that it must cross to reach a region in which it can be removed by convection. The washout rate is also affected by the volumes of the regions through which it is transported. Figure 4a shows the washout of tracer when the cells or the intestine are preloaded with tracer. In each case the plasma flow and all barrier conductances are 1 ml g" min". (For simplicity, intestinal flow is set to zero.)... 

A large change in the conductance of the luminal mucosal cell membrane, PS has only a modest effect on tracer washout of tracer preloaded into the intestinal lumen. Fig. 4b. The curve rises more rapidly, but the washout rate is only slightly greater when the conductance is raised 100-fold. 

Cell tracer transport experiments performed in drug-sensitive KB3-1 cells and KB8-5 cells expressing modest levels of Pgp demonstrated the high sensitivity of the Ga-complex in detecting the outward transport activity of Pgp [139]. The KB3-l-to-KB8-5 uptake ratio was 104 and the washout rate of Ga-complex in KB8-5 cells (k = 0.20 min" ) was 10-fold faster when compared with... 

Be should be a useful tracer in detailed studies of atmospheric transport and washout. It is not produced in significant quantities by nuclear tests, and therefore variations in its activity from year to year should reflect variations in atmospheric processes. Several investigators have measured 7Be at different altitudes and latitudes. As the latitude, altitude, and time variations become better known, it should be possible to calculate precisely the rates of vertical and meridional transport and the rates of deposition at the earth s surface. 

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