Capillary Supply and Metabolism of Muscle Fibers

660

377

SUMMARY1. Five subjects trained for 8 weeks on a bicycle ergometer for an average of 40 min/day, four times a week at a work load requiring 80 % of the maximal oxygen uptake (02maX.)-1o2 max. determinations were performed, and muscle biopsies from the quadriceps femoris muscle (vastus lateralis) were taken before, as well as repeatedly during, the training period. The muscle biopsies were histochemically stained for fibre-types (myofibrillar ATPase) and capillaries (amylase-PAS method), and analysed biochemically for succinate dehydrogenase and cytochrome oxidase activities.2. The training programme resulted in a 16% increase in l2max., a 20 % increase in capillary density, a 20 % increase in mean fibre area, and an approximately 40 % increase in the activities of succinate dehydrogenase and cytochrome oxidase.3. The capillary supply to type I, IIA and IIB fibres, expressed as the mean number of capillaries in contact with each fibre-type, relative to fibre-type area, increased equally.4. The present study shows that endurance training constitutes a powerful stimulus for capillary proliferation in human skeletal muscle.

Section: Capillary Supply Of Different Fibre-typesmentioning

confidence: 89%

Section: Muscle Capillarization and Trainingmentioning

confidence: 99%

Capillary supply of the quadriceps femoris muscle of man: adaptive response to exercise

Andersen¹,

Henriksson²

1977

660

377

“…Many mammalian muscles are heterogeneous mixtures of fibres of widely differing oxidative enzyme activities, and it was first shown by Romanul (1965) that the relation between capillary supply and oxidative activity exists even within these mixed muscles: fibres with a high oxidative enzyme activity generally have a higher capillary density than their more glycolytic neighbours. A method of computing the quantitative difference in capillary supply to fibres within mixed muscles was described by Gray & Renkin (1978), who demonstrated that oxidative fibres received approximately twice the capillary supply density that surrounded the more glycolytic fibres within rabbit fast muscles.…”

Section: Introductionmentioning

confidence: 99%

Changes in capillary distribution in rat fast muscles following nerve crush and reinnervation.

Large¹,

Tyler²

1985

The recovery of muscle weight and contraction tension was measured in rat anterior tibialis muscle following unilateral crushing of the lateral popliteal nerve. Muscle twitch and tetanic tensions and muscle weight had recovered to control values within 6‐8 weeks after the nerve was crushed. Capillary supply to each of the four types of muscle fibre present in the intact muscle, and within the groups of adjacent fibres of similar histochemical reaction for succinate dehydrogenase and myofibrillar actomyosin ATPase found in the reinnervated muscle, was computed by the method of Gray & Renkin (1978). Capillary area density (capillaries/mm2) within the grouped regions of the reinnervated muscle was not significantly different from the supply to the same fibre type in intact contralateral muscles. Capillary/fibre ratio for the more glycolytic fibre types (alpha W, alpha?) was lower than in intact muscle, while the values for both alpha R and beta R oxidative fibres agreed closely with control values. It seems that selective growth and loss of capillaries occurs during reinnervation, adjusting capillary supply to meet the changed metabolic demands of the individual fibres following regrouping.

“…The factor that appears to be common to these experimental conditions is an increased capacity of the muscles to utilize 02, related most probably to an increased 02 consumption. Romanul (1965) and Romanul & Pollock (1969) showed that the capillarity of the muscle fibres was related in a direct way to the oxidative metabolism of the fibres.…”

mentioning

confidence: 99%

The effect of hyperthyroidism on capillarity and oxidative capacity in rat soleus and gastrocnemius muscles.

Capó¹,

Sillau²

1983

SUMMARY1. Muscle fibre composition and capillarity were evaluated in frozen sections stained for myosin ATPase of the soleus and the white area of the medial head of the gastrocnemius of rats made hyperthyroid by injections of triiodothyronine (300-400 ,ug/kg body weight, every other day) for 2, 3 and 4 weeks.2. 02 consumption of homogenates of these muscles in the presence of excess inorganic phosphate (Pi) and ADP with pyruvate and malate as substrates was also measured. 3. Increased oxidative capacity was observed in the soleus homogenates of hyperthyroid animals after 2 weeks of treatment while no changes were observed in the oxidative capacity of the homogenates of the white area of the medial head of the gastrocnemius, even after 4 weeks of treatment.4. Hyperthyroid animals showed a greater capillarity than controls in both muscles. In the soleus this was evident after 2 weeks of treatment while in the white area of the medial head of the gastrocnemius, it was evident only after 4 weeks of treatment.5. Fibre composition was affected in the soleus after 4 weeks of treatment. In control animals two fibre types were present in the soleus: slow-twitch oxidative fibres (s.o. or type I fibres) with a high ATPase activity after acid pre-incubation and fast-twitch glycolytic oxidative fibres (f.o.g. or type IIa fibres) with a low ATPase activity after acid pre-incubation. In the soleus of the hyperthyroid animals, a third fibre type with intermediate ATPase activity after acid pre-incubation was also present. This most probably represents a change in the type of myosin being synthesized by some fibres. No changes in fibre composition were observed in the white area of medial head ofthe gastrocnemius which was made up of only fast-twitch glycolytic fibres (f.g. or type IIb fibres).6. The changes in oxidative capacity and capillarity in the soleus preceded and did not seem to be related to the changes in the type of myosin being synthesized.7. The increased capillarity found in the white area of the medial head of the gastrocnemius of the hyperthyroid animals, in the absence of an increase in the * To whom reprint requests should be addressed.