AJP - Heart and Circulatory Physiology, Vol 243, Issue 2 296-H306, Copyright © 1982 by American Physiological Society
Muscular blood flow distribution patterns as a function of running speed in rats
M. H. Laughlin and R. B. Armstrong
Muscle blood flow (BF) was measured using the radiolabeled microsphere
technique within and among nine major muscles of rats before exercise and
during treadmill walking or running at speeds of 15, 30, 45, 60, and 75
m/min. Measurements were made during exercise after 1 min of steady walking
or running. Male Sprague-Dawley rats were chronically instrumented with 2
Silastic catheters, one in the ascending aorta via the right carotid artery
for microsphere infusion and one in the left renal artery for arterial
reference blood sample withdrawal. The preexercise results demonstrated
that 1) BF to deep slow-twitch muscles was three to four times that to
peripheral fast muscles (e.g., soleus and gastrocnemius BFs were 138 and 33
ml . min-1 . 100 g-1, respectively); 2) BFs to red portions within mixed
muscles were three to four times those to white portions (e.g, red and
white gastrocnemius BFs were 54 and 18 ml . min-1 . 100 g-1, respectively;
and 3) there was a direct relationship (P less than 0.05) between BFs to
muscles and their slow-twitch oxidative fiber populations. The results
obtained during exercise demonstrated that 1) at the slowest speed studied
(15 m/min) BFs to the red portions of muscles increased, whereas BFs to the
white portions of the same muscles decreased; 2) BFs to all muscles (except
soleus) were increased during running at 75 m/min when there was a range of
flows of 30 ml . 100 g-1 . min-1 (white gastrocnemius) to 321 (vastus
intermedius), 3) at all running speeds the increases in BF to muscles were
directly related to the fast-twitch, high-oxidative fiber populations of
the muscles; and 4) BFs to visceral tissues and fat were decreased during
exercise.
