In vivo uptake kinetics of aminoglycosides in the kidney cortex of XXXX .

@entity801 @entity2890 @entity4509 @entity5153 @entity35 @entity4028
The renal cortical uptake kinetics of four aminoglycosides were studied in vivo. @entity801 , @entity5153 , @entity2890 or @entity4509 were administered to @entity35 by continuous infusion over 6 hr achieving constant serum levels ranging from 0.2 to 100 micrograms/ml. Renal cortical concentrations at the end of the infusion were plotted against the steady-state serum levels. Steady-state elevations of serum @entity801 and @entity5153 were associated with nonlinear increases in cortical levels, suggesting saturable uptake. Analysis of the data using Michaelis-Menten kinetics indicates that the apparent Km for @entity801 and @entity5153 were 15.01 and 23.84 micrograms/ml and Vmax 149.83 and 178.36 micrograms/g of cortex per hr, respectively. The "initial" rate of uptake (at serum levels below 15 micrograms/ml) was highest for @entity801 . The cortical uptake of @entity2890 was linearly related to elevations in serum levels [cortex concentration (conc) = 9.24 + 1.40 serum conc]. The initial rate of @entity2890 uptake was considerably lower than that for @entity801 and @entity5153 . For @entity4509 , the initial rate of uptake followed Michaelis Menten kinetics and the second phase of the titration curve was linear. The equation for total @entity4509 uptake was: cortex conc = 12.98 + 1.71 serum conc. Aminoglycosides exhibit differing kinetics for renal cortical uptake in the @entity35 during constant infusions. These results indicate that more than one mechanism probably mediates the uptake of each @entity4028 . Depending on which mechanism predominates, the kinetic pattern may be saturable, linear or mixed.
