Abstract
Abstract In vitro uptake of labelled iodipamide in the presence of a large excess of hippurate is due to a distinct, possibly complex, anion uptake system, the L‐system, present in kidney cortex, ciliary processes and lateral choroid plexus. A large number of organic anions of very different structure, many of them drugs, have now been screened for ability to inhibit the L‐system in rabbit tissues. The L‐system is depressed much more by cholegraphic than by urographic radio‐contrast agents. A majority among substances known to be excreted by the liver depressed the L‐system. Substances of mol.wt. below 175 have little effect, among heavier anions inhibition is common. This size dependence is similar to that for biliary excretion. No structural specificity can be discerned. In all these respects the L‐system is liver‐like. Certain liver‐excreted anions have little effect on the L‐system. This indicates that the organic anion transport system of the liver is composite. The affinity of many drugs to the L‐system is bound to affect their pharmacokinetic behaviour and can give rise to drug interactions.
Published Version
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