Introduction

Blood biochemical profiles are being extensively used in veterinary medicine not only for individual clinical evaluation, but also to assess animals populations, because when properly interpreted, these figures provide important information about animal's clinical status, nutritional balance, deficits situation, treatment evaluation and prognosis (Payne & Payne 1987). Transaminase enzymes, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) catalyses the conversion of the amino acid alanine and aspartate in pyruvate and oxaloacetate, respectively. These enzymes are found in various body tissues, therefore, are not organic-specific (Gonzalez et al 2001). According Thrall (2007), ALT is a specific liver enzyme for dogs and cats, therefore, between liver function tests it is considered the most common and best for liver damage detection. Its half-life is two to three days in dogs (Maia SDa). ALT serum increased activity indicates a cell damage. Small increases in its activity are not relevant, because the degree of liver damage is responsible for the increased ALT activity (Thrall 2007). There are injuries that allow enzyme passage through the membrane without loss of cellular function, for example, hypoxia due shock. There are also some injuries, with a total loss of cellular function in cases of necrosis of hepatocytes, for example, caused by infection of infectious canine hepatitis virus (Thrall 2007). Meyer et al. (1992) added that serum ALT increase is also the processes that alter the hepatocytes membrane permeability, such as aggression by toxins and hypoxia. The AST is an enzyme of greater concentration in mitochondria membranes, and it is also present in a wide variety of tissues and cells of the heart muscle, skeletal and liver (Bush 2004; Thrall 2007), with its half-life approximately 24 hours in dogs (Price & Alberti 1979) and AST has mitochondrial half-life of 87 hours (Panteghini 1990). This enzyme is usually studied to diagnose muscle diseases, because it is not considered a liver specific enzyme, but in its enzymatic activity is considered a good marker of liver damage in horses and cattle (Bush 2004; Thrall 2007). In dogs, because of the short half-life, is used as an indicator of active liver damage, associated to this result the serum ALT activity increase. As well as ALT, may be increased in the enzyme induction in dogs (Maia SDb). Regarding the cell location, ALT is exclusively cytoplasmic, whereas AST is found in both the cytoplasm and mitochondria (Sherwin 1996) and both AST and ALT, usually are present in plasma, in bile, and in CSF saliva and is not found in urine, unless this is a renal injury (Balistreri 1999). The aminotransferases are considered useful in the differentiation between disease and hepatocellular cholestatic process, but in cases of severe liver disease, these two conditions tend to co-exist (Maia SDc). This study aimed to determine serum ALT and AST values in healthy dogs from Belem, Para State, Brazil.

Materials and Methods

In this study were used 50 adult and clinically healthy dogs, both genders, different races, from the metropolitan region of Belém The blood samples were withdrawn by cephalic or jugular vein puncture and then placed in tubes without anticoagulant. After collection blood was centrifuged for 10 minutes at 5000rpm to obtain serum, which was stored in microtubes and kept frozen until evaluation. ALT and AST determination was made by kinetic method, using commercial kits. Values were compared with the reference values established in the specific literature, as Amaral (1994), Kaneko et al. (1997) and Gonzalez (2001). Descriptive statistics such as mean, standard error, standard deviation, minimum and maximum values and coefficient of variation were used.

Results

In this study, we found, for ALT and AST values (UI/L) respectively as follows: average of 31.46 and 30.44, 13.48 and standard deviation of 8.76, standard error of 11.01 and 6.95; minimum values of 15 and 10 and maximum of 62 and 47 and coefficient of variation of 42.87 and 28.77 (Table 1).

Table 1. ALT and AST serum activities in healthy dogs from Belém, Pará State, Brazil, represented as mean, standard deviation, standard error, maximum and minimum values, and variation coefficient, expressed in UI/L. Belém, 2009.

*Alanine aminotransferase
**Aspartate aminotransferase
*** Kaneko el al, 1997

Discussion and Conclusions

Several authors published reference data for different biochemical parameters in dogs, as Amaral (1994), Kaneko et al. (1997) and Gonzalez et al (2001). In this study, ALT values were much higher than reported by Amaral (1994), which found an average of 11.8UI/L. The variability of these parameters in this research, was lower, reaching coefficients of variation of 41.7% and lower values than those described by Gonzales et al 2001, that found values of average, standard deviation, average error and coefficient of variation, respectively of 53.9, 31.9, 4.4 and 57.8UI/L. Mean AST of this experiment within the range recommended by Thrall (2007) and far beyond the values determined by Kaneko (1997), which are respectively 16 to 40 and 6.2 to 13UI/L. For AST, there are few studies to determine their serum levels, probably because its low specificity to liver damage in dogs as described by Thrall (2007), as this enzyme is also found in red blood cells, kidney cells and pancreas, and in smaller quantities, in cardiac and skeletal muscle cells, but more due to its location within the cell, increasing in AST activity indicates severe damage to hepatocytes, with degeneration or necrosis (Maia SDc). Within the blood parameters, the enzyme activity shows great variability (Handelman & Blue 1993). Most of the reference values in the literature is available for foreign authors (Duncan & Prasse 1982; Coles 1986a; Coles 1986b; Kaneko 1989; Medway et al. Apud Matos & Matos 1988; Jacobs et al. 1992), fact that limits its use in animals from northern Brazil. The knowledge of ALT and AST normal values in plasma for specific dogs populations and their variations in Belém, Pará State, Brazil, undoubtedly contribute to a better interpretation of biochemical data from clinical liver these species in this region.

References

1.  Payne JM, Payne S. 1987. The Metabolic Profile Test. New York: Oxford University Press, 179p

2.  González FHD, Carvalho V, Müller VA, Duarte FR. 2001.Perfil bioquímico sang íneo de cães e gatos na cidade de Porto Alegre, Rio Grande do Sul, Brasil. Arq. Fac. Vet. UFRGS. 29:1-6.

3.  Thrall M. Hematologia e Bioquímica Clínica Veterinária 1^st ed. Roca: São Paulo, p. 335-354, 2007.

4.  Maia L. SDa. Bioquimica Clinica (parte 1). Disponível em: Acesso em: 12/01/2009.

5.  Meyer DJ, Coles EH, Rich LJ. Veterinary laboratory medicine. Philadelphia: W.B. Saunders, 1992. Cap. 5: Hepatic test abnormalities, p. 55-70.

6.  Bush BM. Interpretação de resultados laboratoriais para clínicos de pequenos animais. 1^st ed. São Paulo: Roca, 2004.

7.  Price CP, Alberti KG. Biochemical Assessment of Liver Function. In: Wright R, Alberti KG, Karran S, Millward-Sadler GH. Liver and biliary disease--pathophysiology, diagnosis, management. London: WB Saunders, 1979. p. 381-416.

8.  Panteghini M. Aspartate aminotransferase isoenzymes. Clin Biochem, v. 23, p. 311-319, 1990.

9.  Maia L. SDb. Bioquímica Clinica (parte 2). Disponível em: Acesso em: 12/01/2009.

10. Sherwin JE, Sobenes JR. Liver function. In: Kaplan LA, Pesce AJ. Clinical chemistry: theory, analysis, and correlation. St. Louis: Mosby, 1996. p. 514-516.

11. Balistreri WF, Rej R. Liver function. In: Burtis CA, Ashwood ER. Tietz textbook of clinical chemistry. Philadelphia: Saunders, 1999.1449-512.

12. Maia L. SDc. Bioquímica Clinica (parte 3). Disponível em: Acesso em: 12/01/2009.

13. Amaral AS. 1994. Determinação de valores de referÍncia para alanina aminotransferase, fosfatase alcalina, amilase, lipase, proteínas totais, albumina, globulinas e colesterol, para cães da região de Santa Maria, RS. Seminário de Pós-Graduação em Medicina Veterinária. Centro de Ciências Rurais. Universidade Federal de Santa Maria.

14. Kaneko JJ, Harvey JW, Bruss MI. 1997. (Eds.) Clinical Biochemistry of Domestic Animals. San Diego: Academic Press, 932p.

15. Handelman Blue J. 1993. Laboratory data: read beyond the numbers. In: Veterinary Laboratory Medicine: In Practice. Trenton: Veterinary Learning Systems.

16. Duncan J, Prasse KW. Patologia clínica veterinária. Rio de Janeiro: Guanabara-Koogan, 1982. ApÍndice I, p.165-170.

17. Coles EH. Veterinary clinical pathology. 4^th ed. Philadelphia: W.B. Saunders, 1986a. Cap. 8: Carbohydrate metabolism and function of the pancreas and digestive tract, p. 152-170.

18. Coles EH. Veterinary clinical pathology. 4^th ed. Philadelphia: W.B. Saunders, 1986b. Cap. 12: Thyroid function, p. 226-230.

19. Kaneko JJ. Clinical biochemistry of domestic animals. 4.ed. San Diego: Academic Press, 1989. Appendixes, p. 878-901.

20. Medway, et al. Cap. 8: Bioquimica Clinica. In: Matos M. S. & Matos P. F. Laboratório clínico médico-veterinário. 2^nd ed. Rio de Janeiro: Atheneu, 1988, p. 203-238.

21. Jacobs RM, Lumsden JH, Vernau W. Canine and feline reference values. In: Kirk RW & Bonagura JD. Current veterinary therapy XI. Philadelphia: W.B. Saunders, 1992. Appendices, p. 1250-1263.