Hemodynamic and Endocrine Changes Associated with Splenic Reserve Mobilization

Abstract

IntroductionIn theory, splenic reserve mobilization should elicit a cardiopulmonary baroreceptor mediated neuroendocrine response (the Gauer‐Henry reflex).Six intact (IN) and 5 (SP) splenectomized Standardbred mares (421–491 kg, ∼9 yr) performed 10 min of treadmill exercise (80% VO2max) to test the hypothesis that hemodynamic and endocrine responses to exercise would differ between IN and SP horsesMethodsBlood samples were obtained before and at 1, 2, 4, 6, 8 and 10 min of exertion. Right ventricular pressure (RVP), right atrial pressure (RAP), arterial pressure (MAP), heart rate (HR), and cardiac output (CO) were measured and total peripheral resistance (TPR) calculated. Plasma atrial natriuretic peptide (ANP) and vasopressin (AVP) concentrations were measured using RIA. Data analysis used ANOVA for repeated measures and SNK. Significance was set at P<0.05.There were no differences (P>0.05) between IN and SP for any variable at rest. All variables except TPR and RAP increased (P<0.05) during exertion in both IN and SP. Means (±SE) for RAP (18 ± 3 vs. 1 ± 2 mmHg), CO (255 ± 21 vs.177 ± 19 L/min), MAP (147 ± 3 vs. 116 ± 8 mmHg), and ANP (66 ± 3 vs. 50 ± 8 pg/mL) were greater for IN vs. SP horses at 10 min of exertion. Mean plasma AVP (95 ± 19 vs. 23 ± 3 pg/mL) was greater (P<0.05) for SP than for IN horses at 10 min of exertion.Ethical Animal ResearchThe study was approved by the Institutional Animal Care and Use Committee. Sources of funding: Ohio Thoroughbred and Standardbred Research Fund and the New Jersey State Initiative on Equine. Competing interests: none.