EFFECTS OF TYROSINE KINASE INHIBITOR, GENISTEIN, AND PHOSPHOTYROSINE PHOSPHATASE INHIBITOR, ORTHOVANADATE, ON CA2+-FREE CONTRACTION OF UTERINE SMOOTH-MUSCLE OF THE RAT

1. The effects of a protein-tyrosine kinase inhibitor, genistein, and a protein-tyrosine phosphatase inhibitor, orthovanadate, were tested on the Ca2+-free contraction of the estrogen-dominated rat, which has been proved to be induced mainly via protein kinase C entirely independently of Ca2+ 2. Genistein (30 mu M) significantly inhibited the contraction indicating participation of tyrosine kinase activity in the contraction. 3. Orthovanadate caused contraction concentration-dependently and augmented the Ca2+-free contraction at concentrations of more than 1 mu M. The contraction by orthovanadate was not inhibited so significantly by genistein (30 mu M). 4. Possible participation of tyrosine kinase activity in Ca2+-free contraction is discussed in addition to the formerly reported participation of protein kinase C.