Protein binding of L-carnitine family components

L-carnitine and its short-, medium- and long-chain acyl esters constitute the L-carnitine family. These compounds in the body are equilibrated according to a homeostatic equilibrium preserved and, when impaired, restored by a dynamic inter-exchange between L-carnitine and its esters, catalysed by carnitine acyl transferases, and a tubular reabsorption process with differentiated thresholds for each component. The interaction of these compounds with albumin and plasma proteins of rats, dogs and humans was carefully investigated by means of ultrafiltration and gel filtration techniques. Results obtained demonstrate that L-carnitine and its short-chain esters, namely acetyl-L-carnitine and propionyl-L-carnitine, do not interact with either albumin or plasma proteins; octanoyl-L-carnitine interacts in a measurable even if poor extent (12-30%), whereas palmitoyl-L-carnitine, a molecule with a detergent activity, is completely bound to albumin and plasma proteins.