Evaluation of indirect blood pressure measurement, plasma endothelin-1 and serum cortisol in clinically healthy horses

Abstract: Equine metabolic syndrome (EMS) it’s a clinical condition that includes obesity, regional adiposity, insulin resistance (IR) and laminitis. A similar syndrome exists in human medi-cine, the metabolic syndrome (MS), were systemic hypertension also is a prominent fea-ture. The systemic hypertension seen in humans with MS is partly due to a vascular endo-thelial dysfunction with an enhanced endothelin-1 (ET-1) mediated vasoconstriction. There are indications that systemic hypertension might be a feature in EMS as well but if ET-1 is involved in the development of the systemic hypertension in horses is not known. In-creased circulating cortisol levels have also been found in humans with MS. To our knowledge, there are no studies that have measured serum cortisol concentrations in horses diagnosed with EMS, and the question remain whether horses with EMS differ in cortisol concentrations compared to controls. Before blood pressure, plasma ET-1 and serum corti-sol can be evaluated in horses with EMS, it is necessary to test the day-to-day variation of these parameters on clinically healthy horses. The aim of the present study was to evaluate the day-to-day variation of indirect oscil-lometric blood pressure measurements, plasma ET-1 and serum cortisol concentrations in healthy Standardbred and Icelandic horses, and to detect any potential breed differences in theses parameters. Additional aims were to study if transportation could influence the re-sults obtained and to compare the two indirect blood pressure measurement devices, the Cardell® Veterinary Vital Signs Monitor (Cardell) Model 9402, and the HDO Memo Diag-nostic (HDO) horse model 1.35.00. Nine horses of each breed were included in the study. Blood pressure was measured and blood samples were collected between 6 and 9 am on two separate days. Eight of the hors-es (four Standardbred horses, four Icelandic horses) were transported to a new stable were they stayed overnight. On the morning after the transportation, the blood pressure meas-urements and the sampling procedure were repeated. The results showed that indirect blood pressure measurements, plasma ET-1 and serum cortisol all had an acceptable day-to-day variation. There were no differences in mean blood pressure between the two breeds but the Icelandic horses had significantly lower mean serum cortisol and significantly higher mean plasma ET-1 concentrations compared to the Standardbred horses. Plasma ET-1 was significantly elevated after transportation, but the mean serum cortisol and mean blood pressure did not differ from the values ob-tained in the home environment. The results indicate an acceptable day-to-day variation of the tested parameters, but the higher plasma ET-1 concentrations recorded after transportation, might have been caused by a stress response associated with the transportation and being housed in a new environ-ment. The differences detected in plasma ET-1 and serum cortisol between the two breeds might be related to differences in genetic setup, training status as well as management conditions. The tested parameters are all potential candidates for further investigation in horses clinically affected of EMS and a further evaluation of possible breed differences in the tested parameters is desirable.