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.