title: Evidence of a slow-to-fast fiber type transition in skeletal muscle from spontaneously hypertensive rats.
abstract: The histochemical, biochemical, and electrophysiological properties of selected muscles were evaluated in spontaneously hypertensive rats (SHR) and compared with their normotensive Wistar-Kyoto (WKY) counterparts. As early as 4 wk of age, slow muscles (soleus) of SHR displayed a significant alteration in fiber type distribution with a decrease of slow-twitch fibers (from 64 to 53%) and a simultaneous increase of type IIA-fibers (from 19 to 39%). In addition, soleus from young SHR had a significant enhancement of both oxidative (citrate synthase, 3-hydroxyacyl-CoA dehydrogenase) and glycolytic [lactate dehydrogenase (LDH)] capacities, which could be partly related to a capillary rarefaction. During development (from the 4th to the 12-14th wk), in the soleus muscle the histochemical differences between SHR and WKY were amplified, whereas most of the enzymatic differences between strains were abolished, except for a significantly higher LDH activity. These histochemical changes had only marginal repercussions on soleus electrophysiological properties. SHR animals had a significantly higher basal metabolic rate, which could not be accounted for by elevation of thyroid hormones. The origin of the slow-to-fast fiber type transition in slow muscle remains unclear but could be related to the increased level of plasma catecholamines in SHR. Indeed, chronic treatment of rats with a beta 2-receptor agonist has been reported to cause slow-to-fast muscle fiber transition [R. J. Zeman, R. Ludemann, T. G. Easton, and J. D. Etlinger. Am. J. Physiol. 254 (Endocrinol. Metab. 17): E726-E732, 1988].
authors.affiliation: Laboratoire de Physiologie, Faculté de Médecine Grange Blanche, Université Claude Bernard, Lyon, France.
authors.forename: L
authors.initials: L
authors.lastname: Ben Bachir-Lamrini
authors.forename: B
authors.initials: B
authors.lastname: Sempore
authors.forename: M H
authors.initials: MH
authors.lastname: Mayet
authors.forename: R J
authors.initials: RJ
authors.lastname: Favier
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000818:Animals; D002196:Capillaries / Q000473:pathology; D006973:Hypertension / Q000503:physiopathology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000098:blood supply / Q000502:physiology* / Q000503:physiopathology; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D011919:Rats, Inbred Strains / Q000502:physiology*; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism
chemical_list: D014284:Triiodothyronine; D015094:3-Hydroxyacyl CoA Dehydrogenases; D007770:L-Lactate Dehydrogenase; D013974:Thyroxine