Effects of various drugs on the osmotic lysis of rat mast cells.

1. Rat mast cells were exposed to low osmotic pressures to produce a 'non-specific' disruption of the mast cell, with release of histamine along with other intracellular contents. 2. The effect of non-steroidal anti-inflammaotry drugs and various other drugs upon osmotically induced histamine release was examined. 3. Representative non-steroidal anti-inflammatory drugs indomethacin, phenylbutazone and flufenamic acid, the acidic compounds ethacrynic acid, iopanoic acid and probenecid, and the local anaesthetic lignocaine, all caused a dose-dependent facilitation of osmotically induced histamine release compared to controls. All drugs were active at 0.1 mmol/l. 4. The previously observed inhibition of compound 48/80 and the antigen-induced histamine release from rat mast cells by similar concentrations of the drugs used in the present study are unlikely to be due to mast cell plasma membrane stabilization.