Untersuchung von Flußgeschwindigkeiten in der isolierten perfundierten Rattenleber durch Pulsmarkierung mit radioaktiven Substraten und mathematischer Analyse der Auswaschkinetiken

Abstract

The multiple indicator dilution technique is critically evaluated and its application to the isolated, Hb-free perfused rat liver is described. From the results of pulse labeling experiments using indicator substances for the total aqueous space of the liver ([3H]water and [14C]urea) and for the extracellular space ([14C]sucrose, [3H]-inulin and [3H]dextran), the mathematical model of the liver in situ is sufficient to also describe the hemodynamics of the isolated liver perfused with a saline solution. The multiple indicator dilution technique in combination with the available mathematical basis is applicable to the study of transport across the liver cell membrane. The method, is restricted to compounds which are metabolized very slowly, such as D-lactate. A possible extension of this method to metabolic processes is discussed in view of pulse labeling experiments with [3H]- and [1-14C]L-lactate. Since the involvement of metabolism in the available mathematical model is not differentiated and the release of products is not taken into consideration, the method in its present state is not applicable to studies of metabolism. Even the parameters of transport derived by this technique are of limited value, when the transported compounds are rapidly metabolized by reversible reactions. Despite these uncertainties, the transport of L-lactate is 10 times faster than that of D-lactate.