Capillary permeability in skeletal muscle of normal subjects

Capillary diffusion capacity (CDC) and muscle blood flow (MBF) were determined from the anterior tibial muscle in 25 normal subjects by measuring the simultaneous clearance of 133xenon and sodium131iodide. The subjects were divided into two groups: one with a mean age of 31 years and the other with a mean age of 51. The older group had a significantly lower MBF (54.6 +/- 9.0 vs. 64.2 +/- 9.5 ml/100 g/min; p less than 0.05) and a significantly greater CDC (7.6 +/- 1.2 vs. 6.1 +/- 1.3 mol/min; p less than 0.01) than the younger group. There was a significant correlation between the CDC increase and the age of the subjects (r = 0.61; p less than 0.01). Furthermore, MBF decreased with increasing age (r = 0.48; p less than 0.05). No differences were found in MBF or CDC between female and male subjects. The mechanisms of increased capillary permeability are discussed.