Influence of metabolic vasodilatation on blood-tissue diffusion in skeletal muscle

Abstract

Gracilis muscles of dogs were perfused at constant flow with blood containing Rb86, and perfusion pressure (PA) and venous radioactivity (V) measured. Muscular contraction was produced by electrical stimulation of the nerve. During and after contraction there was vasodilatation (decreased PA) and increased Rb86 uptake (decreased V). The same or equivalent changes were observed with tracer flux from muscle to blood instead of from blood to muscle; using K42 instead of Rb , when muscular contraction was done at constant pressure instead of constant flow; and after ischemia, i. e., during metabolic vasodilatation produced without contraction. Maximal increase of capillary transport capacity (PS) for Rb or K was 2[long dash]2. 5-fold, and was associated with vascular resistance (R) slightly greater than minimal. Up to this limit, [DELTA]PS and[long dash][DELTA]R varied directly with contraction frequency and inversely with perfusion rate. Excessive muscular work in relation to blood flow produced a fall in PS. Prolonged exposure to excessive work led to loss of PS response with no impairment of AR.