Liver homogenates, fish

The main organ involved in PCB metabolism and excretion in fish is the liver. Metabolism of PCBs in fish liver homogenates has been demonstrated (29,30,32) and PCB metabolites are excreted into bile (25,28,34). What is not known is extent to which PCB metabolites excreted in bile are eliminated in feces. Also the role of kidneys, gills, intestine and skin in PCB elimination in fish has not been fully elucidated. The only study on urinary excretion of PCBs was in dogfish sharks and revealed that urine was not a major route of elimination (28). 

In an effort to characterize further the metabolism of DEHP by trout, the effect of the mixed function oxidase inhibitor, piperonyl butoxide, upon the metabolism of DEHP by these trout liver fractions and serum was examined. Because of the use of piperonyl butoxide as an insecticide synergist, it is possible that fish might be exposed to this chemical in the environment. The data in Table VII show that piperonyl butoxide inhibited overall metabolism of DEHP by liver homogenates and microsomes whether NADPH was added or not. The hydrolysis of DEHP by serum was also blocked by piperonyl butoxide and although not shown, this was also the case with liver cytosol. These latter results were surprising because piperonyl butoxide has been known as a mixed function oxidase inhibitor only, and would not be expected... 

A drin and Dieldrin Metabolism.— The in vivo metabolism of the chlorinated alicyclic insecticides, aldrin and dieldrin, has been measured. Fish were exposed to l c-labelled aldrin or dieldrin for 6 hours. The metabolism of each compound was monitored by thin layer chromatography of hexane and chloroform-methanol extracts of liver homogenates, followed by liquid scintillation counting of the spots (5,15,16). 

All fish were sacrificed between 5 00 and 9 00 a.m. Washed micro-somes were prepared from liver homogenates as described previously (3). When whole liver homogenates were used as the enzyme source, 10% w/v homogenates were prepared in 0.15 M KC1, 0.02 M HEPES (N-2-hydroxypiperazine-N -2-ethane sulfonic acid Sigma) buffer (pH... 

Precision is measured by making replicate measurements. As mentioned before, it is known to be a function of concentration and should be determined at the concentration level of interest. The intrasample variance can be determined by splitting a sample into several subsamples and carrying out the sample preparation/analysis under identical conditions to obtain a measure of RSD. For example, several aliquots of homogenized fish liver can be processed through the same extraction and analytical procedure, and the RSD computed. The intersample variance can be measured by analyzing several samples from the same source. For example, different fish from the same pond can be analyzed to estimate the intersample RSD. 

Fraction of mercury in diet that is absorbed (A. Radiolabeled methyl-mercuric nitrate was administered in water to three healthy volunteers (Aberg et al. 1969). The uptake was >95%. Miettinen et al. (1971) incubated fish liver homogenate with radiolabeled MeHgN03 to yield a methylmercury proteinate. The proteinate was then fed to fish that were killed after a week, cooked, and fed to volunteers after confirmation of the methylmercury in the fish. Mean uptake exceeded 94%. For the derivation of an MRL, an absorption factor of 0.95 is used. 

With few exceptions 12a-hydroxylation is carried out on Cjy-sterol substrates by a hepatic microsomal enzyme (cf. Chapter 9). Those exceptions include 12a-hydrox-ylation of chenodeoxycholic acid in the python [147], eel [148], chicken [149] and trout [150]. Perfusion of isolated rat liver with chenodeoxycholic acid was reported to provide about 30% of the biliary acids as cholic acid [151]. Taurochenodeoxycho-late was hydroxylated to taurocholate by liver homogenates of cod fish [1[36]. 

Conjugation of phenols, aliphatic and steroid alcohols with sulfate occurs in mammals, birds, reptiles, amphibia, but not in fish. In addition, active sulfate in the presence of transferase will conjugate aromatic amines and form sulfamates [70] in mammals, birds, and spiders. The synthesis of sulfate derivatives occurs in the soluble fraction of liver homogenates through the formation of adenosine-5 -phosphosulfate (APS) and 3 -phosphoadenosine-5 -phosphosulfate (PAPS) [21]. The reactions may be written as follows ... 

BDE 47, 99 100 Fish (Muscle tissues of salmon and conger eel and liver tissues of sea bass) green mussel Homogenization, MSPD with sodium sulfate, microwave-assisted extraction with pentane-dichloromethane (1 1) and purification with GPC Gas Chromatography (DB-5MS) Q-MS <100 ng/Kg [41]... 

Further confirmation of the absence of a receptor analogous to that of mammalian and avian species was obtained from binding studies carried out jLn vitro. Detergent solubilized preparations of freshly prepared homogenates, or acetone dried powders, of fish liver and kidney were assayed for specific binding activity as described previously (2, 3). In no case was it possible to... 

A dehydrogenase is purified to homogeneity from fish liver. The atomic absorption spectrometry shows that the enzyme contains 0.316% (by weight) of zinc. This enables calculation of the minimal molecular weight (Mmin) of the metalloen-zyme according to... 

MeS02-PCBs are initially co-extracted from tissue with other OHS and lipids. Lipid-rich tissues such as adipose, liver and lung have been homogenized with dichloromethane (DCM) and n-hexane/2-propanol (3 2) to co-extract lipid and OHS [95,117, 118]. Tissues have also been homogenized with acetone/n-hexane and extracted with n-hexane/diethyl ether or methyl tert-butyl ether (MTBE) [119]. Mammalian adipose and liver and whole fish have been dehydrated with sodium sulfate prior to extraction with n-hexane/DCM (1 1) [11, 96]. Human liver and feces have been extracted with benzene and refluxing by Soxhlet [120], Formic acid has been added to milk samples in preparation for further cleanup [16], After extraction, OHS and aryl methyl sulfones have been separated from lipids by various techniques. Lipid destructive strategies include saponifi-... 

For organic pollutants extraction, a 5-10 g amount of fish and mussel liver was homogenized with anhydrous sodium sulfate and extracted with n-hexane in a Soxhlet device. The extracts were filtered and concentrated by rotary evaporator (Dobrinas et al., 2004b). 

Seal blubber tends to be pure homogeneous fat and like the fish liver oils can be rendered quite simply. Whale blubber on the other hand contains tough connective tissue and fibres and is now rendered in rotating Kvaerner cookers under high pressure steam. As recently as 1955, world production figures (xlOOO metric tons) for marine oils were whale, 378 sperm, 91 seal, 6.5 fish body, 310 aquatic animal liver, 73 (presumably including whale liver oils as a source of vitamins A and D). By 1989 the figures (xlOOO) were marine mammal oil production, 1 fish liver oil, 32 fish oils, 1593 (Bimbo and Crowther, 1992). 

Kandutsch and Russell (1960) have studied the kinetics of the incorporation of acetate by cell-free homogenates of preputial gland tumors and liver into various sterols and have come to the conclusion that the sequence, lanosterol, 24,25-dihydrolanosterol, 4a-methyl-J -cholestenol, J -cholestenol, 7-dehydrocholesterol, cholesterol, operates predominantly in the tumor tissue, and to some extent in the liver. In the latter tissue, the saturation of the double bond of desmosterol (24,25-dehydro-cholesterol) is thought to be the last step in the biosynthesis (Stokes and Fish, 1960). 

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