INHIBITORY EFFECTS OF PROTEIN-KINASE INHIBITORS AND CYTOSKELETAL INHIBITORS ON CA2+-FREE CONTRACTION OF RAT UTERUS

In rat uterine smooth muscle, sustained Ca2+-free contraction was observed by oxytocin in Ca2+-free solution. This Ca2+-free contraction was effectively inhibited by protein kinase inhibitors and cytoskeletal inhibitors but myosin-light chain kinase (MLCK) inhibitors were not so effective. Simultaneous addition of a protein kinase inhibitor and a cytoskeletal inhibitor caused synergistic inhibition. These results suggest that the mechanism for Ca2+-free contraction involves some protein kinase and cytoskeletal elements rather than MLCK.