Nitrogenous waste, enogenous chemical

shelfish patology

1. SUBJECT - FISH AND SHELLFISH PATHOLOGY TOPIC -NITROGENOUS WASTE, ENOGENOUS CHEMICAL NANAJI DESHMUKH VETERINARY SCIENCE UNIVERSITY JABALPUR (M.P.) COLLeGE OF FISHERY ALPUR SCIENCE

2. Nitrogenous wastes Nitrogenous wastes are synthesized by animals from excess amino acids Unlike lipids and carbohydrates amino acids are not stored in the body They are deaminated by the liver tissues and the amino group has to be excreted.

3. Deamination NH2.CHR.COOH + H2O  NH3 + O CHR.COOH Transaminase Amino acid Water Ammonia Keto acid Toxic, it must be excreted Can be converted into glucose and recycled

4. Three types of nitrogenous wastes are used by the vertebrates Ammonia Urea Uric acid Ammonia is a direct product of deamination. In the liver Urea is produced from ammonia. T his also takes place in the liver tissues 2NH 3 + CO 2  CO(NH 2 ) 2 + H 2 O Uric acid is formed directly from amino acids in a series of reactions that produces its complex ring structure.

5. The use of these three forms of nitrogenous wastes follows a pattern in animals Excreted by insects, most reptiles and all birds Excreted by chondricthyes (sharks and rays), terrestrial amphibians and mammals Excreted mainly by aquatic invertebrates, osteichthyes (bony fish) and tadpoles Insoluble Moderately soluble Highly soluble Not very toxic Moderately toxic Highly toxic C 5 H 4 O 3 N 4 CO(NH 2 ) 2 NH 3 URIC ACID UREA AMMONIA N H H H NH 2 C O NH 2 O O O N N N N

6. ENDOGENOUS CHEMICALS IN FISH TISSUES Endogenous chemicals are those chemicals which naturally occur within biological organisms. These chemicals such as eicosanoids which are derivatives of lipids are involved in many physiological functions. Exogenous chemicals are found outside biological organisms. When exogenous chemicals occur in the environment they can become a hazard to biological life such as interfering with natural physiological processes within organisms. These chemicals can also change the natural chemistry of the environment which could facilitate the spread of organisms which can be hazardous to biological life including fishes in the surrounding area.

7. Endogenous Chemicals in Fish Tissue s Fatty acids Eicosanoids Prostanoid biosynthesis Leukotriene biosynthesis Eicosanoid notation

8. Fatty acids Fatty acids. Fatty acids (FA) are found in fish fat and are the main sources of metabolic energy in fish, as well as being precursors for a group of biologically active compounds known as eicosanoids (Sargent et al., 1999; Sargent et al., 2002). FAs are amphiphilic having a polar section consisting of a hydrophilic carboxyl group and a nonpolar section consisting of a hydrophobic hydrocarbon chain (Figure 1.1). FAs usually contain an even number of carbon atoms in an unbranched chain. A FA containing only C-C single bonds is considered to be saturated. FAs containing at least PREVIEW 2 one C-C double bond are considered to be unsaturated fatty acids (UFAs). FAs containing one double bond are termed monounsaturated fatty acids (MUFAs) and FAs containing more than one double bond are termed polyunsaturated fatty acids (PUFAs). The double bonds are usually in a cis configuration (Campbell and Farrell, 2002)

9. FAs are designated using a numbering system. For example, linolenic acid is designated 18:3n-3. The first number, 18, designates the number of carbons in the chain, the number to the right of the colon designates the number of double bonds in the FA chain, and the n-3 indicates the position of the first double bond from the terminal methyl group. In older literature, an  is used instead of an n (ex. 18:3-3) (Campbell and Farrell, 2002; Sargent et al., 2002)

10. Essential fatty acids Essential fatty acids. Essential fatty acids (EFAs) are FAs which fish or humans are incapable of producing. The human body cannot produce n-3 and n-6 FAs, or convert n-3 FAs into n-6 FAs, or vice versa (Henzl, 1999). Humans, therefore, acquire EFAs through their diet/nutrition. Linoleic acid (LA, 18:2n-6) and linolenic acid (LNA, 18:3n3) are EFAs. LA is a precursor of arachidonic acid (AA, 20:4n-6) and LNA is a precursor of docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3). AA, DHA, and EPA are precursors of eicosanoid synthesis (Bell et al., 1986; Sargent et al., 1995).

11. Eicosanoids. Eicosanoids. Eicosanoids are 20-carbon chained derivatives of fatty acids. Eicosanoids are found in many animal tissues and have many physiological functions. (Buchmann, 1999; Campbell and Farrell, 2002). Eicosanoids are primarily divided into 4 subgroups: prostaglandins (PGs) and thromboxanes (TXs), which are sometimes termed prostanoids, leukotrienes (LTs), and the less biologically active hydroxyeicosatetraenoic and hydroxyeicosapentanoic acids (HETEs and HPETEs) (Mustafa and Srivastava, 1989; Sargent et al., 1999; Campbell and Farrell, 2002).

12. The PUFA requirements for normal growth and development of fish include DHA, EPA, and AA, which are all precursors of eicosanoids (Rowley et al., 1999; Sargent et al., 1999). The main precursor of the biologically active eicosanoids is AA. The eicosanoids produced by EPA and DHA are usually less biologically active. EPA PREVIEW 4 has been shown to inhibit the formation of eicosanoids from AA and to interfere with the actions of eicosanoids formed from AA. Eicosanoid actions in the body can be determined by the AA:EPA ratios. High tissue ratios of AA:EPA result in enhanced eicosanoid actions, whereas high tissue ratios of EPA:AA result in decreased eicosanoid actions (Terano, et al, 1986; Sargent et al., 1999).

13. Prostanoid biosynthesis Prostanoid biosynthesis. Arachidonic acid (AA) is released from its storage site in phospholipids where it reacts with PGH synthase (also referred to as cyclooxygenase). PGH synthase inserts two oxygen molecules into AA, producing a 15-hydroperoxy-9,11- endoperoxide containing a cyclopentene ring (PGG2). PGG2 then is reduced to PGH2. Both PGG2 and PGH2 are very chemically reactive and have half lives of ~3 min. at physiological pH. PGH2 then reacts with other enzymes to form the biologically active prostanoids: Prostaglandin D2 (PGD2), Prostaglandin E2 (PGE2), Prostaglandin F2a (PGF2a), Thromboxane A2 (TXA2), and Prostaglandin I2 (PGI2 or prostacyclin) (Marks,