title: Effects of diet consistency on the myosin heavy chain mRNAs of rat masseter muscle during postnatal development.
abstract: To study the effects of diet consistency on the fiber phenotypes of rat masseter (1-70 days of age), the mRNAs of myosin heavy chain isoforms (MHC embryonic, neonatal, I, IIa, IId/x and IIb) were measured in total RNA preparations from masseters of hard-diet group (HDG) and soft-diet group (SDG) by competitive reverse transcriptase-polymerase chain reaction (RT-PCR). With respect to the time course of the transition of each MHC mRNA expressed as a percentage relative to the maximum mean, the soft diet facilitated early (9 days after weaning) expression of IId/x and IIb isoforms, and also a decline in the expression of neonatal and IIa isoforms. The expression of neonatal, IIa and IId/x isoforms at 70 days of age was significantly (P<0.05, P<0.01, P<0.01, respectively) lower in SDG than in HDG, indicating a higher relative composition of the IIb isoform in the SDG. Embryonic MHC mRNA had disappeared by 14 days of age (i.e. before weaning at 19 days). No MHC I mRNA was observed in any masseter studied. These results suggest that in the rat a soft diet facilitates an even more MHC IIb-rich phenotype in the masseter muscle than a hard diet.
authors.affiliation: Second Department of Oral and Maxillofacial Surgery, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, 230-8501, Yokohama, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Saito
authors.forename: Y
authors.initials: Y
authors.lastname: Ohnuki
authors.forename: A
authors.initials: A
authors.lastname: Yamane
authors.forename: Y
authors.initials: Y
authors.lastname: Saeki
mesh_terms: D000818:Animals; D004032:Diet; D005786:Gene Expression Regulation; D006244:Hardness; D008406:Masseter Muscle / Q000254:growth & development*; D018995:Myosin Heavy Chains / Q000235:genetics*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D024744:Skeletal Muscle Myosins / Q000235:genetics*
chemical_list: D020033:Protein Isoforms; D012333:RNA, Messenger; D024744:Skeletal Muscle Myosins; D018995:Myosin Heavy Chains