Enzyme activities, fibre types and capillarization in calf muscles of patients with intermittent claudication

Abstract

Gastrocnemius muscle samples were obtained from 2 groups of patients with intermittent claudication and from an age-matched control group. Group A consisted of patients with impaired blood flow to both legs, but in group B the patients had arterial occlusions in only 1 leg. Succinate dehydrogenase (SDH) activity was significantly lower in the patients compared to the controls, being 6.4 (A), 5.3 (Boccluded leg), and 5.4 (Bunoccluded leg) vs. 8.7 .mu.mol/g per min in the control group. The average proportions of slow twitch (ST) and fast twitch (FT), fibers in the control group was 60% ST and 40% FT. No patient group differed significantly from this. In the control group the FT population was made up of similar proportions of FTa and FTb fibers, but in group A there were approximately twice as many FTb compared to FTa fibers (2P < 0.05). With the exception of the ST fibers of group A, the area of the 3 fiber types tended to be smaller in the patient groups as compared to the controls (10-20%). Muscle capillarization, expressed as the number of capillaries/fiber, was similar in the 3 groups, 1.48 (control), 1.67 (A), 1.54 (Boccluded leg) and 1.62 (Bunoccluded leg), respectively. Due to the small mean fiber area in group B, capillary density (cap/mm2) in this group was significantly higher than the control value. There were no significant differences between the occluded and unoccluded leg in group B patients with respect to enzyme activities, fiber type distribution, fiber areas or capillary supply. The relatively low oxidative potential of the gastrocnemius muscle is related to a low level of physical activity. A concomitant high degree of capillarization in this patient group indicates different regulatory mechanisms for oxidative enzyme synthesis and capillary proliferation.