B Sjödin

Human soleus muscle: A comparison of fiber composition and enzyme activities with other leg muscles

SummaryThe relationship between fiber composition and enzyme profiles as estimated from in vitro enzyme activities has been studied in human skeletal muscle. Samples from the soleus, gastrocnemius, and vastus lateralis muscles were obtained both by biopsying normal subjects and from patients during nonmuscular related general surgery. The samples were analyzed for fiber composition, phosphorylase (a+b), phosphofructokinase, and creatine phosphokinase activities. The fibers were assigned to two major types based on the histochemical display of alkaline stable myofibrillar adenosine triphosphatase staining. This staining is related to the activity of the enzyme and thus the contractility of the fibers. One fibre type lacks (Type I or slow twitch fiber) and the other one (Type II or fast twitch fiber) contains this enzyme. The soleus muscle contained predominantly slow twitch (Type I) fibers with the mean for all subjects being 80% (range 64 to 100%). In contrast the gastrocnemius and vastus lateralis muscles only contained 57% slow twitch fibers (range 34–82%). The activities of the glycolytic enzymes assayed, except hexokinase, were lower in predominantly slow twitch as compared with muscle with many fast twitch fibers and this was consistent with muscle histochemical staining patterns for alpha glycerophosphate dehydrogenase. Succinate dehydrogenase and creatine phosphokinase activities were not related to fiber distribution.

Distribution of LDH Isozymes in Human Skeletal Muscle

LDH isozyme patterns in human skeletal muscle have been studied in 17 subjects of both sexes and varying age groups (16–55 years). Homogenized muscle biopsy materials have been analysed for total LDH activity (Vmax) in both directions, as well as enzyme activity attributable to isozymes. In addition, different isozymes have been electrophoretically separated and stained. In human skeletal muscle all (5) LDH isozymes were present, although the relative contribution from the more heart-specific isozymes (LDH 1 plus 2) declined the higher the total LDH activity. In absolute terms, however, this decline corresponded to a 2 to 3 fold increase in the activity of LDH 1 plus 2 when the two extremes with low and high total LDH activity, respectively, were compared. Per cent LDH 1 plus 2 of total LDH activity was found to increase with an increase in per cent slow-twitch fibres. As an increase in total LDH activity was synonymous to an increase in per cent fast-twitch fibres, it was concluded that LDH isozyme patte...

Isozymes of Creatine Phosphokinase and Myokinase in Human Heart and Skeletal Muscle

The isozyme patterns of creatine phosphokinase (CPK) and myokinase (MK) were investigated in biopsy material from human heart and skeletal muscle. The protein separation was performed on crude muscle homogenates by means of flat-bed isoelectric focusing. Two isozymes were demonstrated for each enzyme, irrespective of the sampling site. The pI values were, on the average, 9.8 (MK-1) and 8.9 (MK-2), 7.2 (CPK-1) and 6.9 (CPK-2), respectively. MK-1 and CPK-1 constituted an average of 81% and 70% of total staining density for each enzyme, respectively. The relative contribution of MK-1 differed, however. Heart muscle showed the highest values (mean 91%) and vastus lateralis the lowest (mean 74%). The mean value for soleus was 86% MK-1. Furthermore, the percentage of MK-1 present was negatively correlated with the percentage of fast twitch fibres in m. vastus lateralis (r = -0.67). No corresponding differences could be demonstrated for CPK isozyme distribution. In conclusion, it was demonstrated that MK and CPK each occurred as two isozymes in human heart and skeletal muscle, and that the relative distribution of MK isozymes, in contrast to CPK, was related to muscle fibre type composition, and thus to the metabolic profile of the muscle.

Isotachophoresis: A New Technique for Determination of Tissue Metabolite Concentrations

An electrophoretic technique, isotachophoresis, has been adapted for qualitative and quantitative analysis of metabolites in human muscle tissue. Metabolite concentrations exceeding 0.1 nmol X kg-1 wet muslce could be determined in 5-10 mg muscle biopsy samples generally in good agreement with conventional analytical methods.