The role of calcium in fly salivary gland secretion analyzed with the ionophore A-23187

The ionophore A-23187 at a concentration of 10 −6 M stimulates fluid secretion, increases calcium influx and efflux, and alters the trensepithelial potential in the isolated fly salivary gland but causes a fall in cyclic AMP concentration. In this regard, it mimics all the effects of 5-hydroxytryptamine of this tissue, except that 5-hydroxytryptamine causes a rise in cyclic AMP concentration. These data in conjunction with past evidence indicate that calcium, as well as cyclic AMP, is a second messenger in the action of 5-hydroxytryptamine upon fly salivary gland secretion.