title: Androgen receptors and skeletal muscle composition in trotters treated with nandrolone laureate.
abstract: To study the effects of nandrolone laureate (19-nortestosterone) on muscle hypertrophy and concentration of androgen receptors (AR), biopsy specimens were taken from the middle gluteal muscle of 6 Finnhorse trotters (geldings and mares) undergoing training before, immediately after, and 13 weeks after a 14-week treatment with nandrolone. Another 6 similarly trained horses served as controls. An additional 10 mares and 10 geldings were used to study annual variation in muscle concentration of AR. AR was immunohistochemically localized in the nuclei. AR concentration remained constant during the first 14 weeks of the study, but increased significantly during the 13-week follow-up period in both groups. This finding can be explained by the annual variation in AR. In the anabolic steroid (AS)-treated horses, but not in the controls (C), the cross-sectional area of the type I fibres increased significantly during the treatment period, and the percentage of type IIA fibres correlated positively with AR concentration at the end of nandrolone treatment. In the AS group, the concentration of DNA decreased during the 13-week follow-up period, and the percentage of H-chains in the isoenzymes of LDH increased. Protein concentration increased in both groups during the follow-up period. Glycogen content and the activity of citrate synthase in muscle during the study remained unchanged. It can thus be concluded that AS produce differing effects on type I and type II fibres, and the AR concentration in equine muscle may contribute to the change observed in the middle gluteal muscle.
authors.affiliation: Agricultural Research Centre, Equine Research, Ypäjä, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Hyyppä
authors.forename: U
authors.initials: U
authors.lastname: Karvonen
authors.forename: L A
authors.initials: LA
authors.lastname: Räsänen
authors.forename: S G
authors.initials: SG
authors.lastname: Persson
authors.forename: A R
authors.initials: AR
authors.lastname: Pösö
mesh_terms: D045930:Anabolic Agents / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D001823:Body Composition / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006736:Horses / Q000097:blood / Q000378:metabolism* / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000187:drug effects / Q000502:physiology; D009277:Nandrolone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D011944:Receptors, Androgen / Q000032:analysis* / Q000187:drug effects / Q000378:metabolism
chemical_list: D045930:Anabolic Agents; D011944:Receptors, Androgen; D009277:Nandrolone