DISTRIBUTION OF BLOOD-FLOW DURING MODERATE AND STRENUOUS EXERCISE IN PONIES (EQUUS-CABALLUS)

  • 1 January 1983
    • journal article
    • research article
    • Vol. 44  (10) , 1861-1866
Abstract
Blood flow to the brain, heart, kidneys, diaphragm and skeletal muscles was studied at rest and during graded treadmill exercise, using radionuclide-labeled microspheres (15 .mu.m diameter), in 11 healthy adult ponies. Hemodynamic changes brought about by exercise included marked increases in cardiac output, mean aortic pressure, left ventricular end-diastolic pressure and right ventricular systolic and end-diastolic pressures. Blood flow to the brain stem and cerebral hemispheres was unchanged during both moderate exercise (heart rate = 154 .+-. 3 beats/min) and severe exercise (heart rate = 225 .+-. 7 beats/min). Despite marked hypocapnia during severe exercise, cerebellar blood flow increased by 32% above control value (94 .+-. 7 ml/min per 100 g). Myocardial blood flow increased transmurally with both levels of exercise. The endo:epi (inner:outer) perfusion ratio for the left ventricule and the interventricular septum decreased during exercise. It was, however, not different from unity. During severe exercise, renal blood flow decreased to 19% of its control value. Blood flow to the diaphragm exceeded that to the skeletal muscles during both intensities of exercise. Blood flow to the exercising muscles of the brachium and thigh increased by 31-38 fold during moderate exercise and by 70-76 fold during severe exercise. The cardiovascular response to strenuous exercise in the pony apparently included an increase in blood flow to the cerebellum, myocardium, diaphragm and exercising skeletal muscles, while blood flow was diverted away from the kidneys. The pony''s cardiovascular response to severe exercise apparently is similar to that of humans.