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

Abstract

Gastrocnemius muscle samples were obtained from two groups of patients with intermittent claudication as well as from an age-matched control group. Group A consisted of patients with impaired blood flow to both legs, whereas in group B the patients had arterial occlusions in only one leg. Succinate dehydrogenase (SDH) activity was significantly lower in the patients compared to the controls, being 6.4 (A), 5.3 (B_{occluded leg}), and 5.4 (B_{unoccluded leg}) vs 8.7 μmol/g/min in the control group. The average proportions of slow twitch (ST) and fast twitch (FT) fibres in the control group was 60% ST and 40% FT. None of the patient groups differed significantly from this. In the control group the fast twitch population was made up of similar proportions of FT_a and FT_b fibres, whereas in group A there were approximately twice as many FT_b compared to FT_a fibres (2P<0.05). With the exception of the ST fibres of group A, the area of the three fibre types tended to be smaller in the patient groups as compared to the controls (10–20%). Muscle capillarization, expressed as the number of capillaries per fibre, was similar in the three groups, 1.48 (control), 1.67 (A), 1.54 (B_{occluded leg}) and 1.62 (B_{unoccluded leg}), respectively. Due to the small mean fibre area in group B, capillary density (cap/mm²) in this group was, however, 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, fibre type distribution, fibre areas or capillary supply. It is concluded that 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.

Key Words:

• diffusion conditions
• enzyme biochemistry
• histochemistry
• peripheral arterial insufficiency
• skeletal muscle adaptation