Tamiko Suzuki

Relation between inhibition of calmodulin and mediator release from rat mast cells

Cationic drugs that interact with calmodulin such as chlorpromazine, trifluoperazine, W-7 and lidocaine caused dose-dependent release of mediator from rat mast cells. A significant correlation was observed between the effects of test drugs with different structure in causing mediator release and calmodulin inhibition.

Different effects of local anesthetics on calcium influx into rat mast cells.

Lidocaine, W49091, procaine and benzocaine inhibited mast cell secretion induced by concanavalin A and A23187. They inhibited Ca influx stimulated by concanavalin A, suggesting that they inactivate Ca channel of mast cells. Lidocaine and procaine inhibited Ca influx stimulated by A23187, but W49091 and benzocaine did not.

Changes in conformation of spin-labeled calmodulin by phospholipids

Spin-labeled calmodulin was synthesized and the effects of phospholipids on its conformation were examined by ESR spectroscopy. Phosphatidylserine (0.1-1.0 mM) increased the signal intensity of the ESR spectrum of spin-labeled calmodulin and decreased the apparent rotational correlation time in the presence of 0.1 mM CaCl2. This change was reversed by addition of excess calcium, and in the absence of calcium phosphatidylserine did not change the spectrum, suggesting that the change in spin-labeled calmodulin brought about by phosphatidylserine was not induced by a hydrophobic interaction of the two, but by inhibition of the binding of calcium to calmodulin. L-Serine and O-phospho-L-serine had no effect on the ESR signals of spin-labeled calmodulin. The effects of various other phospholipids were also examined. Their inhibitory activities were in the order phosphatidic acid greater than phosphatidylserine greater than phosphatidylglycerol = phosphatidylinositol; phosphatidylethanolamine and phosphatidylcholine had no effect on the spectra. The effects of these phospholipids were dependent on their binding activities toward calcium. Furthermore, phosphatidic acid and phosphatidylserine at 1 mM reduced the activity of calmodulin-dependent phosphodiesterase by 16.4 and 8.7%, respectively. These findings indicate that spin-labeled calmodulin did not interact with the phospholipids by a hydrophobic interaction, but that calcium binding to spin-labeled calmodulin interfered with phosphatidic acid, phosphatidylserine, phosphatidylglycerol and phosphatidylinositol, and some of these phospholipids inactivated calmodulin. Thus the activity of calmodulin may be regulated in part by some phospholipids.

Inhibitory effects of steroidal anesthetics on histamine release from rat mast cells stimulated by concanavalin A, compound 48/80 and A23187

1. Alphaxalone and alphadolone acetate were found to inhibit histamine release from rat mast cells induced by concanavalin A by blocking the calcium channels of the cells. 2. They also both inhibited the release induced by A23187, but only alphaxalone inhibited the release induced by compound 48/80. 3. It is concluded that the inhibitory effects of these compounds were not due to their anesthetic properties, but may have been due to their inhibition of steps of the release cascade that open calcium channels and subsequent steps.