Serum albumin (Felis catus) (CSA)

Serum albumin (Felis catus), also known as Fel d 2, is the most abundant protein in feline plasma and a vital member of the serum albumin family [1]. It is primarily synthesized in the liver and serves two major physiological roles: maintaining the colloid osmotic pressure necessary for proper fluid distribution between the intravascular and extravascular compartments, and acting as a versatile transport protein for a wide array of endogenous and exogenous substances [4]. These substances include long-chain fatty acids, bile pigments, steroid hormones, and numerous pharmacological agents, whose pharmacokinetics are heavily influenced by their affinity for albumin [5]. In veterinary medicine, the high binding affinity of drugs like cefovecin to cat serum albumin is exploited to achieve prolonged therapeutic durations [6]. Beyond its physiological transport functions, cat serum albumin is recognized as a significant minor allergen in humans sensitized to cats [2]. It is particularly noted for its role in 'pork-cat syndrome,' a condition where individuals develop an allergy to pork due to the high degree of structural homology and subsequent IgE cross-reactivity between feline and porcine serum albumins [3]. Clinically, monitoring serum albumin levels in cats is essential for assessing hepatic synthetic function, renal filtration integrity, and overall nutritional status [4]. Alterations in its concentration can significantly impact the free, active fraction of highly protein-bound drugs, necessitating dosage adjustments to avoid toxicity or therapeutic failure [7]. Sources: [1] UniProt P49064; [2] WHO/IWS Allergen Nomenclature (Fel d 2); [3] Posthumus et al. (2013) J Allergy Clin Immunol; [4] Smith, B.P. Large Animal Internal Medicine; [5] Seed, M. (2017) 'The role of serum albumin in drug delivery'; [6] Stegemann et al. (2006) J Vet Pharmacol Ther; [7] Giguere et al. (2013) Antimicrobial Therapy in Veterinary Medicine.

Other names

Fel d 2Cat serum albuminfSAALB

Serum albumin acts as a primary carrier protein that reversibly binds ligands through hydrophobic and electrostatic interactions within specific Sudlow sites (Site I and Site II), thereby regulating the free fraction and distribution of drugs [1][5]. In the context of allergy, it functions as an allergen (Fel d 2) that binds to specific IgE antibodies on the surface of mast cells and basophils, triggering degranulation and the release of inflammatory mediators [2][3].