FETAL MYOSIN HEAVY-CHAIN INCREASES IN THE HUMAN MASSETER MUSCLE DURING AGING

Biochemical, immunohistochemical and molecular biological methods were used to detect fetal myosin heavy chain (MyHC) in the human masseter of elderly and young subjects. Samples from the elderly subjects conta ined larger amounts of fetal MyHC than those of young adults. Only a v ery small amount of embryonic MyHC could be detected in both age group s. Embryonic and fetal MyHCs were never detected in the control adult orofacial, limb and trunk muscles. Polymerase chain reaction (PCR) ana lysis revealed the presence of fetal mRNA sequences in elderly and you ng masseter muscles. We conclude that fetal MyHC is present in the hum an masseter throughout the life span and that there is an increase in the relative amount of this protein with age.