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

Abstract

Technetium 99m-labeled diisopropyliminodiacetic (acid [^99mTc]DISIDA) has been used extensively in the evaluation of hepatobiliary diseases. As a result of investigation into transport mechanisms of [^99mTc]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 ^99mTc from the ⁹⁹Mo column, and the total quantity of ^99mTc eluted. Primary cultures of rat hepatocytes were used to evaluate the transport of Na^99mTcO₄ and the ^99mTc-labeled DISIDA monomer. Pertechnetate was not taken up by the hepatocytes, the amount of [^99mTc]DISIDa taken up was not dependent on the concentration of DISIDA but rather on the concentration of technetium, when the DISIDA/^99mTc 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.