Hemodynamic and Endocrine Changes Associated with Splenic Reserve Mobilization

I n 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% VO 2max ) to test the hypothesis that hemodynamic and endocrine responses to exercise would differ between IN and SP horses Methods Blood 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 Research The study was approved by the Institutional Animal Care and Use Committee. Sources of funding:  Ohio Thoroughbred and Standardbred Research Fund and the N ew J ersey S tate Initiative on Equine. Competing interests:  none.