Principais aspectos e particularidades do metabolismo hepático em felinos domésticos (Felis catus)

Abstract

In feline species, morphophysiology and significant quantities of specific metabolic processes are discussed in the veterinary medical field. Therefore, the aim was to study, through a literature review, the main aspects and particularities of hepatic metabolism in felines (Felis catus). Bile, a product of the liver, is stored in the gallbladder during interdigestive phases and released into the duodenum for emulsification of fatty components. In felines, the components of the biliary tract are the bile ductules, intralobular and interlobular ducts, hepatic canaliculi, cystic duct, gallbladder, and the sphincter of Oddi (an anatomical-physiological channel common in the duodenal papilla of cats). Felines are unable to convert primary bile acids into secondary bile acids by conjugation with glycine in cases of taurine deficiency, which makes them obligatory conjugators of this amino acid, thus characterizing their mandatory dietary requirement for taurine. Physiological and pathophysiological mechanisms have not been elucidated regarding the reaction of cats to Propofol, Acetaminophen, Aspirin, and Piroxicam; metabolic and genetic particularities are factors that explain the singularities, especially concerning the drugs and their administration. Medicinal intoxications, nutritional disorders, and the interpretation of laboratory liver function tests complicate the clinical treatment of feline liver diseases, including Feline Hepatic Lipidosis. Certain agents damage liver tissue acutely; others require bioaccumulation to cause lesions in the liver parenchyma and clinical-pathological changes evidenced by the serum increase of biological markers such as Alkaline Phosphatase, Alanine Aminotransferase, and Aspartate Aminotransferase. A factor impacting the biotransformation of substances is the underdevelopment of the finely tuned microsomal enzymatic system in felines, given that their dietary xenobiotic variation is minimal; the feline liver expresses only two isoforms of the UGT enzyme, UGT1A1 and UGT1A2, and does not express UGT1A6 or UGT1A9. Unable to synthesize linoleic acid, cats do not synthesize arachidonic acid (due to low hepatic expression of ∆-6 desaturase and ∆-5 desaturase). Therefore, it is considered that the biotransformation of drugs in the liver, the deficiency of NAT2 (associated with low acetylation in the feline liver), the faster clearance process, and the reliable interpretation of liver function laboratory tests are topics that should be refined in feline research, ensuring adequate treatment, quality of life, and well-being for the animal.