SKELETAL-MUSCLE MICROCIRCULATORY STRUCTURE AND HEMODYNAMICS IN DIABETES

Within skeletal muscle, insulin-dependent (Type 1) diabetes produces s traighter, narrower capillaries. To test the hypothesis that these mic rovascular alterations would be associated with impaired capillary hem odynamics, intravital microscopy techniques were used to study the in vivo spinotrapezius muscle microcirculation of age-matched control (C) and streptozotocin (STZ) induced diabetic (D) rats. D rats exhibited a marked reduction in body weight (C, 266 +/- 5 g; D, 150 +/- 6 g; P < 0.001). At resting sarcomere lengths (i.e. approximate to 2.7 mu m), the additional capillary length arising from tortuosity and branching was less in D muscle (C, 10.5 +/- 0.8%; D, 5.3 +/- 1.0%, P < 0.01). Ca pillary diameter was reduced in D muscle (C, 5.4 +/- 0.1 mu m; D, 4.6 +/- 0.1 mu m; P < 0.001), and was positively correlated (r = 0.71) wit h the decreased proportion of capillaries sustaining flow (C, 85 +/- 5 %; D, 53 +/- 3%; P < 0.001). Within those 'flowing' capillaries, red b lood cell (RBC) velocity and flux were reduced 29 and 43%, respectivel y in D muscle (both P < 0.05). This reduced calculated O-2 delivery by 57% per unit tissue width and 41% per unit muscle mass. Capillary 'tu be' hematocrit was unchanged from control values (C, 0.22 +/- 0.02; D, 0.22 +/- 0.02). We conclude that, in the diabetic state, microvascula r remodeling is associated with a reduced proportion of 'flowing' capi llaries and a reduction in RBC velocity;and flux in these vessels such that skeletal muscle O-2 delivery is markedly reduced. (C) 1998 Publi shed by Elsevier Science B.V. All rights reserved.