1. Skeletal muscle blood flow is coupled with metabolism; for this coupling
to be effective in matching blood flow to capillary exchange, control of c
apillary blood flow and recruitment must reside at the capillary level.
2. Capillaries are, indeed, capable of sensing and responding to vasoactive
stimuli. We report studies that indicate that contraction of skeletal musc
le fibres underneath capillaries is capable of increasing blood flow in tho
se capillaries.
3. This presumed metabolically related signal initiates remote dilations in
arterioles upstream of the stimulated capillaries. Our findings indicate t
hat the vasodilatory signal is transmitted along the blood vessel wall.
4. Although we present evidence supporting a role for gap junctionally medi
ated communication of this vasodilatory signal, it appears unlikely to be p
rimarily electrotonic spread of membrane potential changes.
5. Our studies further indicate that the transmitted signal is not dependen
t on changes in endothelial cell calcium.