In vitro models for the determination of
drug mode of action
IBAM GbR Dr. Rainer Knörle & Dr. Peter SchnierleFerdinand-Porsche-Str. 5, 79211 Denzlingen
Our service offering includes several models for the identification of the
molecular targets of a drug and of its off-target effects
It has been shown that melanin a pigment found in the skin and other parts of the body has an ability to bind drugs. Drug binding to melanin is causative for a multitude of physiological, pathophysiological or toxic effects in biological systems.
Melanin-containing tissues have been located in various parts of the human body:
• skin• hair• eye• heart• lungs• liver• inner ear• brain substantia nigra (neuromelanin)
Melanin has a multitude of physiological functions dependent on the tissue:
• protection from UV light• sequestering of harmful substances (organic compounds, heavy metals)• redoxpolymer
A contribution of drug-melanin binding is established in several disorders:
• pigment disturbances of skin and hair• ocular toxicity • chorioretinopathy• macular degeneration• ocular phototoxicity• ototoxicity• M. Parkinson• extrapyramidal symptoms• carcinogenicity of drugs• several forms of cancer (malignant melanoma)
Melanin binding also may influence drug delivery in pigmented tissues.
Examples of drugs accumulating in melanin
• β-adrenergics (propranolol, metoprolol, timolol, clenbuterol)• antimalarials (chloroquine)• neuroleptics (haloperidol, risperidone)• antibiotics (amikacin, tobramycin)• benzodiazepines (flunitrazepam)• carcinogenes (benzopyrene)• nicotine and its combustion products• metal ions: iron, copper, lead, nickel
Determination of drug-melanin interaction
IBAM offers a self developed and patented assay based on affinity chromatography for the determination of melanin affinities of drugs.
The advantages of this affinity chromatographic approach are:
• dynamic model: binding to and displacement from melanin can be studied• use of native instead of radiolabelled substances• competing binding studies of two or more drugs to melanin are possible.
The study of drug-drug interactions is of foremost importance in drug safety. Displacement of one drug by another from its binding sites on melanin provokes an increase in the free concentration of the drug with sometimesgrave toxicological consequences.
Binding of the antimalarial drug chloroquine to melanin
examined by frontal affinity chromatography
We offer a characterisation of the pharmacological profiles of drugs. Based on this knowledge, drug effects may be explained and new indications for the drugs may be found.
Binding of a Sideritis scardica
Binding of a ligand to a receptor does not necessarily induce a biological response. Therefore, we offer multiple target functional bioassays using isolated organs, intact cells or cell preparations.
We provide several models to study drug-induced modulation of neurotransmitter and hormone release (amino acids, catecholamines and their metabolites, biogenic amines).
Experiments can be performed with tissue slices, synaptosomes and cell lines.
Effect of the GABA-transaminase inhibitor vigabatrin
Stimulation of noradrenaline release from rat brain slices
Inhibition of serotonin uptake in JAR cells
Enzymes are excellent targets for pharmacological intervention, owing to their essential roles in life processes and pathophysiology. Not surprisingly, enzymeinhibitors represent almost half the drugs in clinical use today.
Diseases treated with enzyme inhibitors are as diverse as
• cancer,• depression, • pain, • cardiovascular diseases, • and erectile dysfunction.
Enzyme inhibition is a strategy, that can correct enzyme substrate deficiencies or an excess of enzyme product formation.
In recent years, the enzymatic modification of biological macromolecules (e.g. phosphorylation or acetylation of proteins) has come into the focus of drug research. Currently, we establish assays for these enzymes.
We offer assays for several enzymes involved in neurotransmittersynthesis and breakdown, including
• acetylcholinesterase• butyrylcholinesterase• GABA transaminase• monoamine oxidases and others.
Assays can of course also be performed with non-CNS enzymes.
We are glad to provide you a specially designed enzyme assay for your pharmacological problem
Inhibition of porcine pancreatic lipase by orlistat
Inhibition of Pseudomonas fluorescens GABAse
Your pharmacological questions - Our answers
You assume that your drug or drug candidate of interest acts on a specific molecular target.
Contact us and IBAM will suggest you suitable series of experiments, i.e.
• test conditions,• test tissues (ex vivo, cell culture, etc.), • measuring parameters, and will conduct these experiments.
On completion of the study you obtain a scientific report of the results.
Do not hesitate to contact us. Our expert team will find the solution for your pharmacological problem.
IBAM GbRDr. Rainer Knörle 6 Dr. Peter SchnierleFerdinand-Porsche-Str. 579211 Denzlingen
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Reprinted from Issue 2 • 2004 Editorial Domperidone Warning: Important or Importation? Here you have it! The perfect example of how profits and politics influence health care. The recent statements from the Food and Drug Administration (FDA) about domperidone are so obviously motivated by politics and profits that the potential impact on health takes a back seat. (See relate