AJP - Regulatory, Integrative and Comparative Physiology, Vol 243, Issue 3 245-R250, Copyright © 1982 by American Physiological Society
Comparison of the response of muskrat, rabbit, and guinea pig heart muscle to hypoxia
T. McKean and R. Landon
Papillary muscles were removed from anesthetized muskrats and rabbits and
mounted in a muscle chamber maintained at 29 degrees C. Muscles were
stimulated at a rate of 12/min and subjected to 30 min of hypoxia followed
by 30 min of reoxygenation. Peak tension in muskrats declined less than
peak tension in rabbits during oxygen deprivation. During reoxygenation,
peak tension in muskrats rapidly returned to control levels and then
exceeded control, whereas peak tension in rabbits never recovered. Time to
peak tension was largely unaffected in muskrats during hypoxia and
decreased in rabbits. During reoxygenation, time to peak tension increased
in muskrats and returned to control in rabbits. Hearts from muskrats and
guinea pigs were removed under ether anesthesia and perfused retrograde
with a physiological saline solution. Developed tension, heart rate,
coronary blood flow, and lactate dehydrogenase (LDH) output were monitored.
During 30 min of hypoxia, muskrat hearts developed a profound bradycardia
compared to guinea pigs. Coronary flow increased in both species but less
so in muskrats. Guinea pig hearts developed contracture whereas muskrat
hearts relaxed. During reoxygenation heart rate and coronary blood flow
returned toward normal but cells released large amounts of LDH, indicating
cell damage. It is concluded that the isolated heart of the muskrat, a
diving mammal, is better able to deal with hypoxia than the heart of the
nondividing guinea pig and rabbit.
