Assessment of plasma carnitine concentrations in relation to ceroid lipofuscinosis in Tibetan Terriers

To determine whether the late onset form of inherited ceroid lipofuscinosis (CL) in Tibetan Terriers is accompanied by low plasma carnitine concentrations prior to the appearance of clinical signs. 129 healthy Tibetan Terriers, 12 Tibetan Terriers with CL, and 95 healthy purebred dogs of other breeds. After withholding food, blood samples were collected from all dogs into tubes containing EDTA. Blood samples were analyzed for plasma-free carnitine and acyl-carnitines concentrations. Neither the mean plasma total carnitine concentration nor the mean fraction of carnitine in the free form differed significantly between Tibetan Terriers with CL and healthy Tibetan Terriers. Among Tibetan Terriers and the general dog population, plasma carnitine concentration increased with age. Castrated males had an overall increase in plasma carnitine concentrations and variability, compared with sexually intact males. By comparison, plasma carnitine concentrations were not significantly different between spayed and sexually intact females. The mean plasma carnitine concentration in the Tibetan Terriers was approximately 22% higher than in the general population of healthy dogs of other breeds. Contrary to what is seen in early onset CL in English Setters and in humans with some forms of CL, plasma carnitine concentrations are not decreased in the late-onset disorder in Tibetan Terriers. Our large-scale study establishes reference range values for plasma carnitine concentrations in dogs as functions of age and sex that will be useful in evaluating potential carnitine deficiencies in other disorders in dogs.