title: Effects of sequential injections of hepatocyte growth factor and insulin-like growth factor-I on adult rabbit extraocular muscle.
abstract: OBJECTIVE
  To determine whether hepatocyte growth factor (HGF) and insulin-like growth factor-I (IGF-I) have synergistic effects in promoting extraocular muscle fiber growth and force generation.
  
  
  METHODS
  A superior rectus muscle of adult rabbits was treated with either a single injection of HGF or sequential injections of HGF followed 1 week later by IGF-I. One week after HGF alone and 1 week after the IGF-I injection, the superior rectus muscles from treated and control orbits were examined for alterations in force generation as well as changes in myofiber size.
  
  
  RESULTS
  Injection of HGF alone did not result in changes to muscle force, specific tension, or myofiber cross-sectional area; however, it did result in a significant increase in numbers of satellite cells. Sequential injection of HGF and IGF-I resulted in significantly increased force, specific tension, and myofiber cross-sectional areas as well as increased numbers of satellite cells.
  
  
  CONCLUSIONS
  Preinjection with HGF augments the treatment effect of IGF-I. This synergistic effect is likely a result of HGF-induced activation of satellite cells and should allow a reduction in IGF-I dosing required to produce a given increase in extraocular muscle force generation.
authors.affiliation: Department of Ophthalmology, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Christy L
authors.initials: CL
authors.lastname: Willoughby
authors.forename: Steven
authors.initials: S
authors.lastname: Ralles
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Christiansen
authors.forename: Linda K
authors.initials: LK
authors.lastname: McLoon
mesh_terms: D000818:Animals; D004357:Drug Synergism; D017228:Hepatocyte Growth Factor / Q000008:administration & dosage / Q000494:pharmacology*; D007124:Immunoenzyme Techniques; D007273:Injections, Intramuscular; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000494:pharmacology*; D009119:Muscle Contraction / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D053580:Muscle Strength / Q000502:physiology; D018995:Myosin Heavy Chains / Q000378:metabolism; D016900:Neurofilament Proteins / Q000378:metabolism; D009801:Oculomotor Muscles / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051763:PAX7 Transcription Factor / Q000378:metabolism; D011817:Rabbits; D032496:Satellite Cells, Skeletal Muscle / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
chemical_list: D016900:Neurofilament Proteins; D051763:PAX7 Transcription Factor; D017228:Hepatocyte Growth Factor; D007334:Insulin-Like Growth Factor I; D018995:Myosin Heavy Chains