Urine shark

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). 

Our initial interest was in studying the disposition of phenol red in the shark. This turned out to be a good choice because nearly equal amounts of the model compound appeared in the urine and bile. After solving the body fluid collecting problems, we studied in greater depth, the transport properties of phenol red in both the renal and hepatic systems. 

Table V contains data for two model substances, p-aminohippurate (PAH) and phenol red. Consideration of the highest values in this table tells you where the major portions of the substances appear. For example, urine and bile show the largest concentrations of PAH and phenol red. Both compounds appear in significant concentrations in the kidney while the values in muscle, brain and cerebrospinal fluid (CSF) are invariably lower than the values seen in plasma. The values in parentheses (Table V) are percent of the administered dose in a given tissue or fluid compartment. They add to the previous information by revealing the overall importance of a particular compartment in the disposition of a substance. For example, while the hepatic concentrations of PAH and phenol red at 4 hrs. are only about 2-fold those of plasma, the large size of the shark liver relative to its body weight, typically about 10%, leads to the appearance of 30-40% of these substances in the liver. The relative handling of these compounds by the urinary and biliary system is obvious from considering the percentage figures. Thus in 24 hours phenol red is about equally distributed in the bile and urine (38 vs 31%) the urinary route is the dominant route of excretion of PAH, i.e., 56 vs 2%.

Information regarding the distribution of the very commonly used detergent sodium lauryl sulfate (SLS) also appears in Table V. Twenty-four hrs. after injection of the form of SLS, most of it (65%) has been excreted in the urine of the shark. At the earlier time point, 4 hrs., the hepatic tissue has a higher concentration and quantity of the detergent than any other tissue. Muscle retained the isotope longer than did other tissues in this table and may represent sulfur exchange with endogenous substances. 

Not surprisingly, much research in sharks, skates and rays has focused on the responses of sharks to human body odors. Human blood attracts sharks, while sweat does not, and urine was even slightly repellent (Tester, 1963). Practitioners use whale meat and mixtures of fish meal and fish oils as shark attrac-tants. In both carnivorous and herbivorous bony fish (Osteichthyes) smell deals with prey odors, social odors, and chemical stimuli in homing, and it is mediated by the first cranial nerve, the olfactory nerve. By contrast, taste serves in detection and selection of food and avoidance of toxic food, and it employs the facial, glossopharyngeal, vagal, and hypoglossal nerves. 

Occurrence and Properties.—Urea occurs as a normal constituent in animal urine to the amount of about 2 per cent in man. It was discovered in 1773. Its physiological significance will be considered later. It is also found in small amounts in the blood and lymph of animals. In the blood of sharks it is present in as large amounts as in human urine. Urea is a beautifully crystalline solid easily soluble in water and in alcohol. It melts at i32°-i33° and sublimes in a vacuum at i20°-i30°. 

Urinary Catheter. An appreciable amount of drug as parent or metabolites may be excreted in the urine of fish. A number of studies have demonstrated that glucuronide, sulfate and taurine conjugates are excreted by the fish kidney as a result of anion/cation carrier-mediated mechanisms (44,45). Urine has been collected for xenobiotic studies in a variety of fish species including flounder (46), dogfish shark (47), rainbow trout (Kleinow, K.M. Can. J. Fish Aq. Sci., in press) and catfish (48). In large measure urine production is greater in freshwater fish as compared to marine species. 

Cannon, J.R., Edmonds, J.S., Francesconi, K.A., Raston, C.L, Saunders. J.B., Skelton, B.W. and White A.H. (1981). Isolation, crystal structure and synthesis of arsenobetaine. a constituent of the western rock Lobster Panulirus cygnus, the dusty shark Carcharhinus obscurus and some samples of human urine. Aust. J. Chem. 34(4), 787-798. 

Cannon, J.R., J.S. Edmonds, K.A. Francesconi, C.L. Raston, J.B. Saunders, B.W. Skelton, and A.H. White Isolation, Crystal Structure and Synthesis of Arse-nobetain, a Constituent of the Western Rock Lobster, the Dusky Shark, and Some Samples of Human Urine. Aust. J. Chem. 34, 787 (1981). 

The active inositols (I and II) are found in small amounts only but their methyl ethers are widespread in Nature. A fourth isomer, scy//o-inositol or scyllitol (IV), has been found in such diverse sources as the cocos palm, shark and dogfish, and in mammalian urine. 

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