Effects of diet consistency on the myosin heavy chain mRNAs of rat masseter muscle during postnatal development

• Published in: Archives of oral biology Vol. 47; no. 2; pp. 109 - 115
• Main Authors: Saito, T., Ohnuki, Y., Yamane, A., Saeki, Y.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2002
• Subjects: Animals; Competitive RT-PCR; Dentistry; Development; Diet; Diet consistency; Gene Expression Regulation; Hardness; Masseter muscle; Masseter Muscle - growth & development; Myosin heavy chain; Myosin Heavy Chains - genetics; Protein Isoforms - genetics; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - analysis; Skeletal Muscle Myosins - genetics; Myosin heavy chain; Masseter muscle; Development; PCR, polymerase chain reaction; RT, reverse transcription; Diet consistency; Competitive RT-PCR
• ISSN: 0003-9969; 1879-1506
• DOI: 10.1016/S0003-9969(01)00094-2

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.