Changes in uterine myosin isozymes from goat during early pregnancy.

Changes in the expression of native myosin, myosin heavy chains (MHCs) and myosin light chains (MLCs) were investigated in goat uterus during early pregnancy. Electrophoresis of native myosin under non dissociating conditions displayed two isozymes differing in their proportions during gestation. Three MHC isoforms were obtained following sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Whereas 204 kDa (a smooth muscle MHC) and 196 kDa (a non muscle MHC) were recorded in uterus from non pregnant goat, uterus of pregnant goat displayed a third 200 kDa smooth muscle MHC. Two conspicuous proteins (154 and 140 kDa respectively) in addition to MHCs were also obtained when the myofibrillar extracts were analysed either in the presence or absence of proteolytic inhibitors. Non pregnant goat uterus showed a basal level (ca.5%) of phosphorylation of regulatory myosin light chain. Uterine myosin from pregnant goat was recorded in a completely dephosphorylated state.