[The mechanisms of elimination of o-125I-benzoate in rabbits]
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R Richter1, A Láznícková, M Láznícek
1Katedra farmakologie a toxikologie farmaceutické fakulty Universizity Karlovy, Hradec Králové.
Abstract:
An analysis of the mechanisms of elimination of o-125I-benzoate in the rabbit kidney on the basis of the inhibition of the secretionary transport by probenecid has shown that o-125I-benzoate is eliminated in the kidneys not only by glomerular filtration but by tubular secretion as well. An effect on the total amount of the drug excreted in the urine is exerted by tubular resorption (apparently by the process of passive diffusion), which exceeds tubular secretion. A comparison of the chromatograms of the plasma and urine before and after the competitive inhibition of the tubular active transport by probenecid revealed a higher share of o-125I-benzylglucuronide in the urine in the case of inhibition. The results suggested a partial share of the kidneys in total biotransformation of o-125I-benzoate. Excretion of the original drug and metabolites in the bile forms a negligible share (less than 1%) of total clearance in rabbits.
Insights
The rabbit kidney eliminates o-125I-benzoate via glomerular filtration and tubular secretion, with tubular reabsorption playing a significant role. The kidneys also contribute to the biotransformation of o-125I-benzoate.
Area of Science:
- Pharmacokinetics and Drug Metabolism
- Renal Physiology
- Toxicology
Context:
- Understanding drug elimination pathways is crucial for predicting drug efficacy and toxicity.
- The rabbit kidney model is frequently used to study renal drug transport and metabolism.
- o-125I-benzoate serves as a model compound for investigating renal excretion mechanisms.
Purpose:
- To elucidate the mechanisms of o-125I-benzoate elimination in the rabbit kidney.
- To determine the contributions of glomerular filtration, tubular secretion, and tubular reabsorption to renal clearance.
- To investigate the role of the kidney in the biotransformation of o-125I-benzoate.
Summary:
- o-125I-benzoate undergoes elimination in the rabbit kidney through both glomerular filtration and active tubular secretion.
- Tubular reabsorption, primarily via passive diffusion, exceeds tubular secretion and influences the total amount of drug excreted.
- Inhibition of tubular secretion by probenecid revealed an increased proportion of o-125I-benzylglucuronide in urine, suggesting renal biotransformation.
- Biliary excretion of o-125I-benzoate and its metabolites is minimal in rabbits (<1% of total clearance).
Impact:
- This study clarifies the complex renal handling of o-125I-benzoate, highlighting the interplay between filtration, secretion, and reabsorption.
- Findings contribute to a better understanding of drug disposition in the kidney and potential sites for drug interactions.
- The data provides insights into the renal contribution to xenobiotic metabolism, relevant for drug development and safety assessment.