Reactive hyperemia in individual capillaries of skeletal muscle.

BURTON, K.. S., AND P. C. JOHNSON. Reactive hyperemia in individual capillaries of skeletal muscle. Am. J. Physiol. 223 (3) : 517-524. 1972.-Red cell velocity profiles in individual capillaries were studied in the sartorius muscle of the cat during reactive hyperemia using a dual-slit photometric system. The velocity profiles varied considerably from each other and from the simultaneously measured volume flow. The profiles were divided into four groups on the basis of the duration of reactive hyperemia following a 60-set occlusion and the time required to attain peak velocity. One group showed almost no response. A second group had a long period of increased flow (60 & 8 set) and reached a peak value in 35 & 16 sec. The duration of reactive hyperemia for the third group (22 ~fr 3 set) was comparable to that of the gross flow (28 of= 6 set) and reached its peak value after 10 rt 4 sec. The peak response in the fourth group occurred after 5 =t 3 set as compared with 6 =t 1 set in the gross flow and was followed by an interval of zero flow (7 =I= 3 set) before returning to normal. The distributions of the 57 capillaries studied were 28, 14, 2 1, and 37 %, respectively. The question of whether reactive hyperemia was due to the opening of new capillaries or to increased flow in previously open capillaries was investigated. Comparing the ratio of peak velocity to control for the average of all flowing capillaries (1.5 : 1) with that of the gross flow (1.8:1), we conclude that augmentation of Aow in previously open capillaries is the primary source of reactive hyperemia.