Importance of precise determination of technetium-labeled DISIDA concentrations for in vitro hepatocellular transport studies

Abstract Technetium 99m-labeled diisopropyliminodiacetic (acid [ 99m Tc]DISIDA) has been used extensively in the evaluation of hepatobiliary diseases. As a result of investigation into transport mechanisms of [ 99m Tc]DISIDA, we undertook to determine precise concentrations of this compound in the standard clinical formulation. Calculations based on published formulas were used. These take into account column efficiency, the time since the previous elution of 99m Tc from the 99 Mo column, and the total quantity of 99m Tc eluted. Primary cultures of rat hepatocytes were used to evaluate the transport of Na 99m TcO 4 and the 99m Tc-labeled DISIDA monomer. Pertechnetate was not taken up by the hepatocytes, the amount of [ 99m Tc]DISIDa taken up was not dependent on the concentration of DISIDA but rather on the concentration of technetium, when the DISIDA/ 99m Tc ratio was varied in the culture medium. We conclude that calculation of the total technetium concentration is necessary to determine the amount of compound taken up by the liver, and to interpret kinetic studies of hepatocellular transport mechanisms.