MYOSIN ISOFORMS IN UTERINE SMOOTH-MUSCLE DURING PREGNANCY IN RAT

Effects of uterine stretching and physiological hypertrophy on myosin isozyme were investigated in rat during pregnancy. Both nonpregnant an d pregnant rat uteri express a single myosin band on native gels. Anal ysis of native myosin under denaturing conditions revealed two myosin heavy chains (MHCs) with molecular mass of 204 and 200 kDa respectivel y. Filamin, a 240 kDa protein co-electrophoreses with myosin on native gels. No correlation is found between regulatory myosin light chain p hosphorylation and pattern of myosin isozymes or the MHC. The results suggest that uterine stretching and physiological hypertrophy during p regnancy do not induce any changes in uterine myosin isozyme.