Creatine Kinase (CK) isoenzymes in dogs, cats, sheep and horses

Most studies on creatine kinase (CK; EC 2.7.3.2) isoenzymes are focused on the myocardial (CK-MB) or on the muscle isoenzyme (CK-MM). A rough estimate of CK-MM activity can be obtained by the routine measurement of total serum CK activity and CKMB can be accurately measured by immunoenzymatic methods. Nevertheless, the brain isoenzyme (CK-BB) and the ‘‘macro-isoenzymes’’ Macro CK-1 (dimer between CK-BB and IgG) and Macro CK-2 (mitochondrial CK) can only be measured by expensive and time-consuming methods or, more practically, by electrophoretic separation. The aim of this work is to define the normal distribution of CK isoenzymes in dogs, cats, sheep and horses by histochemical detection of the isoenzymes on gel electrophoresis (ISO-CK, Sebia, Firenze, Italy), and to preliminarily assess the possible role of CK-BB isoenzyme in identifying neurologic disorders. The study was done on 132 sera from 56 sheep (15 with Coenurus cerebralis), 31 dogs (3 with CNS tumours), 23 cats (6 with neurological feline infectious peritonitis) and 12 horses (2 with compressive CNS disorders). In healthy animals, bands corresponding to CK isoenzymes were intense in sheep and horses, moderate in cats and weak in dogs, likely due to the different activity of total CK in serum of these species. All the isoenzymes except CK-MB were detectable in sheep; CK-MM, macro-CK2 and CK-BB were found in horses; CK-MM, macro- CK1 and, occasionally, CK-MB were evident in cats; CK-MM and, occasionally, macro-CK2 and/or CK-BB were expressed in dogs. Finally, in all the species except cats the intensity of the CKBB band increased in animals with neurologic disorders. These results demonstrate that the electrophoretic distribution of CK isoenzymes varies with species and encourage further investigatation of the role of CK-BB as a biomarker of CNS disorders.