title: Role of local contractile activity and muscle fiber type on LPL regulation during exercise.
abstract: The purpose of this study was to determine the influence of local contractile activity on lipoprotein lipase (LPL) regulation in skeletal muscle. Short-term voluntary run training increased LPL mRNA concentration and LPL immunoreactive mass about threefold in white skeletal muscles of the rat hindlimb (all P < 0.01). Training also increased total and heparin-releasable LPL enzyme activity in white hindlimb muscles and in postheparin plasma (P < 0.05). Training did not enhance LPL regulation in a white muscle that was not recruited during running (masseter). LPL levels were already high in red skeletal muscles of control rats, and training did not result in a further rise. In resting rats, local electrical stimulation of a motor nerve to a predominantly white muscle caused a significant rise in LPL mRNA, immunoreactive mass, and enzyme activity relative to the contralateral control muscle of the same animals (all P < 0.01). Finally, LPL expression was several times greater in a red muscle (soleus) of rats with normal postural activity than rats with immobilized hindlimbs (P < 0.01). In summary, these studies support the hypothesis that local contractile activity is required for increasing LPL expression during exercise training and for maintaining a high level of LPL expression in postural muscles.
authors.affiliation: Integrative Biology, Pharmacology, and Physiology, University of Texas Health Science Center-Houston, Houston, Texas, 77030, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Hamilton
authors.forename: J
authors.initials: J
authors.lastname: Etienne
authors.forename: W C
authors.initials: WC
authors.lastname: McClure
authors.forename: B S
authors.initials: BS
authors.lastname: Pavey
authors.forename: A K
authors.initials: AK
authors.lastname: Holloway
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006493:Heparin / Q000494:pharmacology; D006614:Hindlimb; D007103:Immobilization; D008071:Lipoprotein Lipase / Q000235:genetics / Q000378:metabolism*; D009043:Motor Activity / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000145:classification / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology; D010805:Physical Conditioning, Animal; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012420:Running / Q000502:physiology
chemical_list: D012333:RNA, Messenger; D006493:Heparin; D008071:Lipoprotein Lipase