Effects of tyrosine kinase inhibitors on voltage-dependent Ba(2+) currents in the guinea-pig gastric antrum.

We have investigated whether tyrosine kinases modify the activity of voltage-dependent Ba(2+) currents (I(Ba)) recorded from guinea-pig gastric myocytes by use of patch-clamp techniques. All experiments were carried on single smooth muscle cells, dispersed from the circular layer of the guinea-pig gastric antrum. Genistein ( > or = 10 microM), a specific tyrosine kinase inhibitor, reduced the peak amplitude of I(Ba) in a voltage- and concentration-dependent manner. Daidzein ( > or = 30 microM), an inactive analog of genistein, also inhibited I(Ba) in a concentration-dependent manner. Similarly, other types of tyrosine kinase inhibitors (lavendustin A and tyrphostin 23) suppressed the peak amplitude of I(Ba) in a concentration-dependent manner. These results indicate that tyrosine kinases may be essential to regulate Ca(2+) mobilization through voltage-dependent Ca(2+) channels in gastric myocytes.