Distribution patterns of blood flow in the rabbit tenuissimus muscle in response to brief ischemia and muscular contraction.

The distribution of the microvascular blood flow in the tenuissimus muscle of the rabbit was examined by intravital microscopy during postocclusion (reactive) hyperemia (RH) elicited by 5 min of circulatory arrest and postexercise (functional) hyperemia (FH) elicited by 1 min of muscular contraction. The main feeding arterioles in this muscle supply two vascular areas--the muscle capillaries and vessels in adjacent connective tissue. From flow measurements made at two different sites in these arterioles, the fractional distribution of the blood flow between the muscle capillaries and the connective tissue at rest and during hyperemia was determined. Both stimuli elicited profound hyperemic responses lasting for approximately 3 min with peak flow values of 7.6 (RH) and 5.5 (FH) times the control flow. There was no major change in the fractional distribution of the hyperemic blood flow in response to the brief ischemia from that observed under resting conditions. Muscular contraction, on the other hand, resulted in a considerably greater increase in the flow to the muscle capillaries than in that to the connective tissue. Differences in reactivity between larger and smaller arteriolar segments within the muscle tissue were considered to underlie the fractional redistribution seen in response to this stimulus. Differential control of arteriolar blood supply and capillary perfusion may thus be exerted by these vascular segments and may be of functional importance in the adjustment of flow to increased tissue oxygen demand.