Effect of oestrogen on myofibre size and myosin expression in growing rats

Abstract

This study examined the effect of oestrogen deprivation and replacement on plantaris muscle size and myosin heavy chain (MHC) isoform composition in rats during a period of physiological growth. Seven-week-old female Sprague-Dawley rats were assigned to one of the three treatment groups: (1) control animals (Sham); (2) ovariectomized animals without oestrogen replacement (OVX/CO); and (3) ovariectomized animals with 17β-oestradiol replacement (OVX/E 2 ). OVX/CO and OVX/E 2 animals were pair-fed with Sham animals to rule out the potentially confounding effects of differences in food intake and weight gain. Rats were killed 4 weeks after surgery and the plantaris muscle was removed for analysis. Ovariectomy had no effect on muscle fibre size, but reduced the relative amount of type IIx MHC. This was reversed with oestrogen replacement, suggesting that the reduction in type IIx MHC expression was an oestrogen-mediated effect. Oestrogen replacement reduced type IIb MHC expression and fast muscle fibre size. Changes in fast fibre size and type IIb MHC expression were not seen with ovariectomy, indicating that these changes were not simply due to the presence of oestrogen in the ovariectomized, oestrogen-replaced animals. These results suggest that another ovarian hormone may counteract the effect of oestrogen on fast fibre size and type IIb MHC expression in intact animals.

Effect of daidzein, 4-methylbenzylidene camphor or estrogen on gastrocnemius muscle of osteoporotic rats undergoing tibia healing period

“…Estrogen fed animals consumed less than others (13 vs 15 g/rat per day respectively) which is in accordance with previous studies (Piccone et al 2004). This may contribute to the lowest BW in these rats, but is not the only reason.…”

“…It was demonstrated that ovarian hormone deficiency could play a role in the failure to recover muscle mass after a period of inactivity of the muscle (Sitnick et al 2006). The presence of estrogen receptors in skeletal muscle indicates that skeletal muscle function is also regulated by estrogen (Piccone et al 2004). Changes in hormone concentration have profound influence on muscle fibers.…”

“…Changes in hormone concentration have profound influence on muscle fibers. Ovariectomy in growing rat resulted in an increase of the diameter of all fiber types in muscles, whereas, estrogen replacement reduced the size of all types of fibers (Piccone et al 2004). In muscles of mature female rodents, estrogen has been associated with modulation of muscle fiber types (Kadi et al 2002, Feng et al 2004, whereas, the crosssectional areas of all types of fibers were not affected by estrogen status (McClung et al 2006, Moran et al 2007.…”

Estradiol modulates myosin regulatory light chain phosphorylation and contractility in skeletal muscle of female mice

“…How the effects of E 2 may differ among fibers with various isoforms of the myosin heavy and light chains is not presently clear, nor is the impact of estrogen status on expression of the various myosin isoforms. There are reports of OVX-related shifts toward slower isoforms/fiber types (11,22,42), toward faster isoforms/fiber types (29,45,61), and no changes in myosin isoforms/fiber types (9,39,42,47,66). Importantly, when such shifts are detected they are modest, in the magnitude of 10% or less, and thus likely have little impact on the extent of force potentiation reported here.…”

Sex-related Differences in Skeletal Muscle Amino Acid Concentrations in 20 Week Old Turkeys

“…In vitro and in vivo studies with a use of animal models and humans have demonstrated that testosterone stimulates skeletal muscle protein synthesis and increases muscle mass (Grigsby et al, 1976;Griggs et al, 1989;Rooyackers and Nair, 1997;Bhasin et al, 2001). On the other hand, ovarian hormones may inhibit muscle protein synthesis and muscle growth (Toth et al, 2001;McCormick et al, 2004;Piccone et al, 2005). During growth of meat type turkeys under current farming conditions, very rapid skeletal muscle protein synthesis results from intensive anabolic processes of amino acids.…”