Abstract
The present study was performed in order to elucidate the histochemical properties of intact rat quadriceps muscles and the differential effect of tenotomy of the patellar tendon on one-joint muscles: vastus medialis muscle (VM), vastus intermedius muscle (VI) and a two-joint muscle: rectus femoris muscle (RF).
Thirty-four white adult female Wistar strain rats weighing 250-300 g were used in this study. The patellar tendon of the right limb was tenotomized and the contralateral limb was served as a control. At the same time, histochemical observations were made on ten normal rat quadriceps muscles. VM, VI and RF muscles from six animals each were excised at intervals of 3, 6, 9 and 12 weeks after tenotomy. Fresh frozen serial cross sections were stained with hematoxylin and eosin (HE) and ATPase activities were observed.
The results obtained were as follows:
(1) The mean diameter of the type I fibers in the deep portion of the quadriceps muscles was larger than that in the superficial portion in the control rats (p < 0.05).
(2) In the control study, a higher proportion of type II fibers was observed in the superficial portion of RF and VM muscles. On the other hand, a higher proportion of type I fibers was observed in the deep portion of the same muscles.
(3) Three weeks after tenotomy, both type I and II fibers of one-joint muscles, VM and VI, were seen to be smaller in diameter than normal (p < 0.01), but histological changes were only slightly noticeable. These changes included the appearance of central nuclei, opaque fiber (early necrotic fibers) and hypertrophic (atrophic) fibers. Six weeks after tenotomy, an increase in the diameter of muscle fibers was seen. In 9 th and 12 th weeks after tenotomy there were some hypertrophic fibers found.
(4) Three weeks after tenotomy, there was only a slight decrease seen in type II fiber diameter of RF. However, in the 6 th week there was a moderate decrease seen in the type I fiber diameter in the deep portion of RF.
Based on these results, it seems likely that the histochemical properties of the intact rat skeletal muscle and the differential effect of tenotomy on one-joint and two-joint muscles are dependent upon anatomical position and functional utilization.
