INFLUENCE OF TYPE AND BREED OF HORSE ON SERUM OSTEOCALCIN CONCENTRATION, AND EVALUATION OF THE APPLICABILITY OF A BOVINE RADIOIMMUNOASSAY AND A HUMAN IMMUNORADIOMETRIC ASSAY TO MEASURE THE HORMONE

Objectives-To evaluate applicability of a human osteocalcin (OC) immun oradiometric assay (IRMA) for use with equine serum and compare it wit h a bovine radioimmunoassay (RIA) previously proven valid for such sam ples, and to describe the effect of type and breed of horses on serum OC concentration. Animals-100 healthy horses of either sex, classified as type I or II (draught or warmblood, respectively). Each type was r epresented by 2 breed groups, each comprising 25 horses. Procedure-Blo od samples were collected in the morning, and the serum was separated. Osteocalcin was measured, using commercially available RIA and IRMA k its, according to the manufacturer's instructions. Ail samples were ev aluated in duplicate. Results-The human IRMA did not recognize equine OC. Significant variations in the bovine RIA results were observed bet ween types of horses. Draught horses had lower OC concentration, compa red with warmblood horses. Significant difference was not observed bet ween breeds for type of horse. Sex had no influence on serum OC values , but age was a significant covariable for both types of horses. Concl usions-No crossreactivity exists between the equine and human amino- a nd/or carboxy-terminus of OC, using this particular human IRMA kit. Di fference in blood OC concentration exists between draught and warmbloo d types of horses. Clinical Relevance-Use of this human IRMA kit is no t valid for equine serum. Horse type must be taken into account when e valuating OC concentration in research or clinical situations, especia lly if small variations in OC concentration are expected.