Inhibition by Hippurate and Probenecid of in vitro Uptake of Iodipamide and o‐Iodohippurate. A Composite Uptake System for Iodipamide in Choroid Plexus, Kidney Cortex and Anterior Uvea of Several Species

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Abstract
Slices of kidney cortex and liver, pieces of lateral choroid plexus and of ciliary body with or without iris were incubated in a potassium‐rich medium containing labelled iodipamide often together with labelled o‐iodohippurate. Tissues were from rabbits, guinea‐pigs, monkeys (3 species), dogs, cats and chicken. Iodipamide at 0.5—2 μM depresses uptake of labelled iodipamide by rabbit kidney cortex wthout affecting uptake of o‐iodohippurate. Hippurate at 30 mM suppresses uptake of o‐iodohippurate in all tissues tested but leaves a fraction of iodipamide uptake in all tissues and species tested. The findings with o‐iodohippurate uptake are compatible with a single uptake system, the findings with iodipamide and the kinetics derived for this substance are incompatible with a single uptake system. Iodipamide seems to be accumulated by one hippurate‐sensitive system shared with o‐iodohippurate and at least one other, hippurate‐insensitive system. This latter system usually is a minority system in kidney cortex and anterior uvea but dominates in liver and choroid plexus and in cat kidney cortex. The hippurate‐insensitive system can be suppressed by probenecid but needs a higher concentration than the hippurate‐sensitive one.