Endogenous substances

Monoamine Oxidase Inhibitors. MAOIs inactivate the enzyme MAO, which is responsible for the oxidative deamination of a variety of endogenous and exogenous substances. Among the endogenous substances are the neurotransmitters, norepinephrine, dopamine, and serotonin. The prototype MAOI is iproniazid [54-92-2] (25), originally tested as an antitubercular dmg and a close chemical relative of the effective antitubercular, isoniazid [54-85-3] (26). Tubercular patients exhibited mood elevation, although no reHef of their tuberculosis, following chronic administration of iproniazid. In... 

The method was validated in accordance to the guidelines of the international conference on harmonization (ICH). Data with respect to accuracy, within- and between run precision, recovery, detection and quantitation limits were reported and found to be within the accepted international criteria. Neither endogeneous substances nor the commonly used dmgs were found to interfere with the retention times of the analytes. Standard solutions of the dmg and quality control preparations at high and low level concentrations were demonstrated to be stable at room temperature and/or -20°C for long and short periods of time. 

Agonist. A compound that elicits a biologic response by mimicking an endogenous substance. 

Antagonist. A drug that blocks the biologic effects of an endogenous substance or exogenously applied drug. 

Receptor. A macromolecule with which a drug or endogenous substance interacts to produce its effect. 

Endogenous substances such as serotonin, amino acids, purines, and pyrimidines all have biological activity and are tolerated in the human body. Therefore, these can be used in some cases as starting points for synthetic drugs. For example, the amino acid tryptophan and neurotransmitter... 

Neurotransmitter Endogenous substance involved in the transmission of nerve impulses. 

A substance cannot be considered as a NT unless it is released. Unfortunately, although it may be possible to show the presence of a substance and some effect when it is applied directly to neurons its release may not be measurable for technical reasons. This is even more true if one strives for the ideal of demonstrating the release of an endogenous substance by physiological stimuli. 

PLC studies in the field of medicine cover the processes of separation, purification, and determination of xenobiotics or endogenous substances present in body fluids and tissues. Such research is carried out with the following aims ... 

The basic aim of PEC applications in clinical chemistry, apart from the recovery of standards of endogenous substances, consists of structural identification of isolated (without further separation) substances of relatively high purity. Therefore, the majority of works devoted to this topic pertain to semipreparative separation. Obtaining low amounts of analytes, achieved by coupling TEC with modem... 

Nonmodified silica gel is used most commonly for the separation of substances of medical interest. The separation is based on the interactions (hydrogen bonding, van der Waals forces, and ionic bonding) between the molecules of drugs, lipids, bile acids, etc., and the silica gel. Alumina has similar properties but is rarely used. Successful separation of endogenous substances, drugs, or their metabolites can also be achieved using physically or chemically modified silica gel. 

Numerous endogenous substances and commercially available pharmaceuticals are racemic mixtures. Therefore, it is an important problem of clinical chemistry to develop methods for resolution of enantiomers and for establishing enantiomeric purity, because these substances exhibit different biological and physiological... 

QUESTION If the oxidation of dopamine is proving to be toxic, are there any natural endogenous substances or nutrients that can help prevent that ... 

Endorphins are found primarily in the limbic system, hypothalamus, and brainstem. Enkephalins and dynorphin (in smaller quantities) are found primarily in the periaqueductal gray matter (PAG) of the midbrain, the limbic system, and the hypothalamus. These endogenous substances mimic the effects of morphine and other opiate drugs at many points in the analgesic system, including in the dorsal horns of the spinal cord. 

In addition to the passive diffusional processes over lipid membranes or between cells, substances can be transferred through the lipid phase of biological membranes through specialized systems, i.e., active transport and facilitated diffusion. Until recently, the active transport component has been discussed only for nutrients or endogenous substances (e.g., amino acids, sugars, bile acids, small peptides), and seemed not to play any major role in the absorption of pharmaceuticals. However, sufficient evidence has now been gathered to recognize the involvement of transporters in the disposition of pharmaceuticals in the body [50, 127]. 

Keppler, D. and J. Konig. Hepatic secretion of conjugated drugs and endogenous substances. Semin. Liver Dis. 2000, 20, 265-272. 

In a bioanalytical method, analyses of blank samples (plasma, urine, or other matrix) should be obtained from at least six sources. Each blank sample should be tested for the possible interference of endogenous substances, metabolites, or degradation products. The response of the peaks interfering at the retention time of the analyte should be less than 20% of the response of a lower quantitation limit standard, and should be less than 5% of the response of the internal standard that was used [18, 19]. For dissolution studies, the dissolution media or excipients should not give a peak or spot that has an identical Rt or Rf value with the analyte [20]. 

TRPV4 was identified a decade ago as an osmotransducer that is expressed in lung, heart, kidney, airway muscle cells, sensory neurons, brain, skin, gut, sympathetic nerves, inner ear, endothelium, and fat tissue [58-61]. TRPV4 is activated by heat (27-34°C), endogenous substances such as anandamide (59, AA) and the arachi-donic acid metabolite 5,6-epoxyeicosatrienoic acid (60, 5,6-EET), a plant dimeric diterpenoid bisandrographolide A (61, BAA), and the semisynthetic phorbol ester 4a-phorbol-12,13-didecanoate (62, 4a-PDD) [62],... 

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