title: Morphological and functional characteristics of skeletal muscle fibers from hormone-replaced and nonreplaced postmenopausal women.
abstract: We tested the hypothesis that cross-bridge mechanisms of contraction differed in early postmenopausal women who did or did not receive hormone replacement therapy (HRT). Vastus lateralis biopsies were obtained from 17 postmenopausal women (49-57 years old), 8 of whom were on HRT for the previous 24 +/- 5 months and 9 of whom were never on HRT. Electrophoresis and enzyme histochemistry revealed that fiber myosin heavy chain (MHC) isoform distribution, the cross-sectional area (CSA) of slow and fast fibers, and the relative CSA occupied by each, were similar for HRT and non-HRT groups. Single permeabilized fibers containing type IIa MHC had greater Ca(2+)-activated peak specific force, unloaded shortening velocity, and peak power than fibers containing type I MHC, but in all cases the values for HRT and non-HRT groups were similar. In this cross-sectional study, we found no evidence that Ca(2+)-activated fiber function, MHC isoform distribution, or relative CSA occupied by slow and fast fibers differed between HRT and non-HRT groups.
authors.affiliation: Department of Exercise and Sport Science, Oregon State University, Corvallis 97331, USA. jeff.widrick@orst.edu
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Widrick
authors.forename: Gianni F
authors.initials: GF
authors.lastname: Maddalozzo
authors.forename: Danielle
authors.initials: D
authors.lastname: Lewis
authors.forename: Beth A
authors.initials: BA
authors.lastname: Valentine
authors.forename: Dena P
authors.initials: DP
authors.lastname: Garner
authors.forename: Julian E
authors.initials: JE
authors.lastname: Stelzer
authors.forename: Todd C
authors.initials: TC
authors.lastname: Shoepe
authors.forename: Christine M
authors.initials: CM
authors.lastname: Snow
mesh_terms: D000886:Anthropometry; D001707:Biopsy, Needle; D016022:Case-Control Studies; D046508:Culture Techniques; D004587:Electrophoresis, Agar Gel; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000378:metabolism* / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000187:drug effects* / Q000378:metabolism; D017698:Postmenopause / Q000187:drug effects*; D011336:Probability; D020033:Protein Isoforms / Q000187:drug effects* / Q000378:metabolism; D012016:Reference Values; D012494:Sampling Studies; D012680:Sensitivity and Specificity
chemical_list: D020033:Protein Isoforms; D018995:Myosin Heavy Chains