LIPOPROTEIN METABOLISM IN DOGS AND CATS

High-density lipoproteins (HDL) are the predominant lipoproteins in pl asma of dogs and cats and are the major cholesterol-carrying particles . Two HDL subfractions are identifiable in dog: small, dense particles (equivalent to human HDL(3)) and large, buoyant particles called HDL( 1), which overlap in hydrated density with low-density lipoproteins (L DL). The HDL(1) are enriched in cholesterol and apolipoprotein (ape) E , and are prevalent in dogs fed high amounts of cholesterol and, or, s aturated fat, when they are also referred to as HDL(c). Lipoproteins s imilar to human HDL(2) and HDL(3) are identifiable in feline plasma, a long with trace HDL(1). Lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyl transferase (LCAT) activities are prese nt in dogs and cats. Both species lack significant cholesteryl ester t ransfer protein activity, and reverse cholesterol transport is probabl y accomplished by receptor-mediated hepatic uptake of HDL(1). Methods for the measurement of canine and feline plasma lipoprotein-cholestero l concentrations, apolipoprotein concentrations, and the activities of LPL, HL and LCAT have been developed. Together with oral and intraven ous fat tolerance tests, these methods provide the basis for studying lipoprotein metabolism in cats and dogs.