Mammalian organ distribution

Toxicokinetics is the study of the rates of absorption, distribution, metabolism, and exaction of substances. Metabolism describes all the processes by which a particular substance is handled in the human body. Literature studies are available on the behavior of several alkyl —glycosides in the mammalian organism. Octyl—D-[U- C]-glucoside, [l- C]-dodecyl— D-maltoside, and [ - ]-hexadecyl— D-glucoside were used as test substances representative of alkyl polyglycosides [109]. The toxicokinetic studies demonstrated that alkyl polyglycosides are physiologically compatible. 

Nakajima T, Matsubayashi T, Kakimoto Y et al (1971) Distribution of hypusine, JV -(4-amino-2-hydroxybutyl)-2,6-diaminohexanoic acid, in mammalian organs. Biochim Biophys Acta... 

The preceding survey of mammalian organs which have sialidase activity indicates that it is broadly distributed and may be an integral component of all organs containing sialyl compounds. 

Superoxide dismutases (SODs) are a family of cytosolic metalloenzymes that specifically remove (reviewed by Omar etal., 1992). SOD distribution within the body is ubiquitous, being found in erythrocytes as well as most organs and cell types. Three distinct mammalian SOD forms exist CuZnSOD, MnSOD and extracellular SOD (EC-SOD). Their amino-acid sequences differ as well as the transition metals at their active sites. Rheumatoid synovial fluid contains low levels of SOD activity and hence little protection from ROM generated by infiltrating PMNs (Blake etcU., 1981). Furthermore, leucocytes from patients with RA are deficient in MnSOD, which might promote the extracellular leakage of O2 (Pasquier et al., 1984). 

In normal human subjects, some 25 % of total body iron (800-1000 mg) is present in the storage forms, mostly as ferritin. Whereas it is likely that all mammalian cell types contain some ferritin, haemosiderin in normal subjects is essentially restricted to cells of the reticuloendothelial system. Ferritin turns out to be almost universal in its distribution ferritin and ferritin-like proteins have been found in all organisms except for one or two archaebacteria. In contrast, haemosiderin has not been found to any extent outside of iron-loaded animals, except for a brief report of a phytosiderin in pea seeds (Laulhere et ah, 1989). 

As observed in mammalian models, the immune system of fishes is a sensitive target organ system to evaluate toxicity. For a more thorough review of environmental immunotoxicology in fishes, with reference to specific classes of xenobiotics, readers are referred to several reviews that deal with the subject over a span of nearly three decades [45-47, 54-57], While fish in the environment may be exposed to a variety of xenobiotics, the most frequently investigated xenobiotics are the polycyclic aromatic hydrocarbons (PAHs) and halogenated aromatic hydrocarbons (HAHs) due to the presence and activation of the aryl hydrocarbon receptor (AhR) in fish, and heavy metals due to their ubiquitous environmental distribution. 

The carbonyl reductases catalyze reduction of aldehydes and ketones by reduced pyridine nucleotides (NADH and/or NADPH). As mentioned earlier, alcohol dehydrogenase can perform this function in the presence of a high ratio of NADH to NAD+. Other enzymes capable of carbonyl reduction include the aldehyde and ketone reductases. The aldehyde and ketone reductases have a ubiquitous species distribution, with the enzymes present in organisms ranging from bacteria to vertebrates. The mammalian carbonyl reductases have been extensively reviewed (101). 

Organ blood flow and organ concentration - organ blood flow is an important factor which determines the distribution of a xenobiotic once it has been absorbed. This flow is related to blood pressure and while mammalian pressures are around 100 mm Hg, fish species usually are about one-fifth or less of this value. 

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