The Effect of Testosterone on Gastrocnemius Muscle Fibres in Growing and Adult Male and Female Rats: A Histochemical, Morphometric and Ultrastructural Study^†

Abstract

In this study, the effect of testosterone on gastrocnemius muscle fibres in growing and adult rats (male and female) was examined using histochemical, morphometric and ultrastructural techniques. After physiological saline (PS), olive oil (OvO) or olive oil + testosterone (OvOT) injections on 72 rats (growing and mature, 36 male and 36 female), the sample tissues of fibre types of the gastrocnemius muscle taken were examined by histochemical [alkaline adenosine triphosphatase (alk-ATPase), acid ATPase (ac-ATPase)], morphometric and ultrastructural techniques. In PS-injected control groups, the gastrocnemius muscle of both sexes contained all the fibre types studied [slow-oxidative muscle fibres (type I), fast-oxidative glycolytic muscle fibres (type IIA) and fast-glycolytic muscle fibres (type IIB)]. The type I fibres had the smallest diameter, type IIA had a medium diameter and type IIB fibres had the largest diameter. In OvO-injected groups, it was observed that the OvO had little effect on the gastrocnemius muscles of either sex, although there was significant enlargement of type IIB fibres. After the injection of OvOT, hypertrophy of muscle fibres was determined by morphometric study. The biggest increase in diameter was on type I fibres. In addition, degenerations on some mitochondria, accumulation of lipid droplets on type I and type II fibres, an increase in glycogen particles, bifurcation of myofibrils, an increase in the number and diameter of units resembling T tubules and an increase in ribosomal content were also observed in the same group by transmission electron microscope. Consequently, it was determined that testosterone can induce protein synthesis in gastrocnemius muscle fibres, and induces changes in shape and size, and also can change the appearance and the number of fibres.

Targeting muscle signaling pathways to minimize adverse effects of androgen deprivation

“…The rodent studies used a large variety of skeletal muscle groups, and not all muscles respond to androgen deprivation or testosterone administration in the same way (Ustunel et al 2003, Serra et al 2013b, De Naeyer et al 2014, Rana et al 2014b. The levator ani is highly responsive to androgen deprivation, reducing in mass by up to 85% after orchiectomy (Oner et al 2008, Rana et al 2014b.…”

“…The levator ani is highly responsive to androgen deprivation, reducing in mass by up to 85% after orchiectomy (Oner et al 2008, Rana et al 2014b. In contrast, limb muscles (i.e., triceps, extensor digitorum longus) are less responsive (Ustunel et al 2003, Serra et al 2013b, De Naeyer et al 2014. In humans, the relative androgen sensitivity of muscle groups such as levator ani is not known, therefore, responsiveness may yield similar patterns or be entirely different.…”

Androgen-mediated improvement of body composition and muscle function involves a novel early transcriptional program including IGF1, mechano growth factor, and induction of β-catenin

“…AR is detectable in bone and muscle cells, but levels are low compared with reproductive tissues such as the prostate and levator ani muscle (Antonio et al 1999, Monks et al 2004. Nevertheless, castration in rats reduces contractile force in muscles of the hindlimb (Brown et al 2001) and produces ultrastructural signs of degeneration and reduced protein synthesis (Ustunel et al 2003). Treatment with anti-androgens limits gains in muscle strength during weight training (Ruzic et al 2003).…”

Effects of nandrolone on recovery after neurotization of chronically denervated muscle in a rat model

“…48,50 When given at supraphysiological doses, anabolic steroids have been shown to increase protein synthesis and ribosomal content in muscle cells, decrease protein breakdown, and stimulate the proliferation and integration of satellite cells. 12,13,39,56 Based on this promising literature support, a preliminary investigation into the potential role of anabolic steroids in augmenting reinnervated muscle cells was undertaken. 22 Rats treated with nandrolone following reversal of established denervation atrophy regained 72% muscle contraction force (vs 57% for the control group).…”

“…19,48 The exact mechanism is not entirely worked out, but theories include a direct effect on net protein synthesis, 13,56 an increase in stem cell activity, 48 or both. Fiber type proportions are not thought to change.…”