AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 5 1177-R1183, Copyright © 1990 by American Physiological Society
Renal and systemic hemodynamic responses to sustained submaximal exertion in horses
K. W. Hinchcliff, K. H. McKeever, L. M. Schmall, C. W. Kohn and W. W. Muir 3rd
Department of Veterinary Physiology, College of Veterinary Medicine, Ohio State University, Columbus 43210.
We investigated the effects of 1 h of sustained submaximal exertion on the
renal and systemic hemodynamics of six horses. The horses ran on a
treadmill at a speed that produced heart rates of 55-60% of each horse's
maximum heart rate. Exertion produced heart rates of 121 +/- 6.6 and 126
+/- 6.1 (SE) beats/min after 15 and 60 min, respectively. Cardiac output
increased significantly (P less than 0.05) from 70.1 +/- 3.1 to 246.2 +/-
4.7 ml.min-1.kg body wt-1 after 15 min of exertion and thereafter did not
change. There was no significant change from rest in p-aminohippuric acid
and creatinine clearances, filtration fraction, or renal blood flow during
exertion. Plasma total solid concentration and hematocrit increased by 3.8
and 8.6%, respectively, between 20 and 60 min of exertion. Pulmonary artery
temperature increased significantly from 37.6 degrees C at rest to 38.6
degrees C at 60 min of exertion. This study demonstrates the ability of the
horse to maintain renal hemodynamics similar to resting values and systemic
hemodynamics at steady-state values despite hemoconcentration and increased
body temperature during sustained submaximal exertion.
