EFFECT OF THROMBIN ON ION CONDUCTANCE OF PERITONEAL MAST-CELLS

The effect of thrombin on ion conductance of rat peritoneal mast cells was studied using the parch-clamp technique. During on-cell recording, no channel activity was usually observed. Addition of 4 nM thrombin to the bathing solution evoked in 10 min the activation of cation channels. Their apparent conductance was within 40 to 330 pS and they had several subconducting states. During whole-cell recording in control, step changes in membrane potential induced chloride and nonselective ionic currents. The average ion conductance of mast cells was 0.9 nS. Thrombin at 0,4-4 nM induced an approximately two-fold conductance increase in about 2-5 min. This effect was probably due to the activity of nonselective channels whose conductance, recorded in the cell-attached configuration, was 250, 180, 100 and 50 pS. Thrombin at a concentration of 0,01-4 nM induced a simultaneous increase in cell conductance and capacitance. DIP-thrombin was shown to have the same effect, which points to the hormone-like activity of thrombin. The data suggest that ion channels activated after a delay in thrombin application might participate in secretion in mast cells.