Effect of muscular exercise on the skeletal muscles of hypothyroid young albino rats: a light and electron microscopic study

ABSTRACT

Intact thyroid axis and regular muscular exercise appear to be needed for normal muscular growth. Twenty eight young male albino rats were used in the present study to evaluate the effect of muscular exercise on the skeletal muscles of hypothyroid rats. Specimens were obtained from the gastrocnemius muscles. Animals were divided into 2 major groups. Group I served as a control group. Group II was the experimental group and was subdivided into subgroup IIa which was formed of hypothyroid rats and Subgroup IIb which was formed of hypothyroid rats that were subjected to muscular exercise in the form of swimming for 20 minutes /day for 15 days. Hypothyroidism was induced using carbimazole orally in a dose of 0.05mg/kgm for 15 consecutive days. Hypothyroidism resulted in marked affection of the gastrocnemius muscle. The muscle fibers were seen to be fragmented and contained pyknotic nuclei. There was a statistically highly significant reduction in the mean thickness of the muscle fibers. Glycogen granules were seen to be accumulated inside the muscle fibers. The gastrocnemius myofibrils appeared to be separated by wide gaps that were filled with glycogen. Muscular exercise in the form of swimming resulted in improvement of the muscle fibers of the gastrocnemius muscle. So regular muscular training is recommended in cases of hypothyroidism in young age for normal development of the skeletal muscles