Neomycin and Spermine Have Similar Effects on Secretion and Phosphoinositide Metabolism in ATP-Depleted Permeabilized Adrenal Chromaffin Cells

Abstract

To evaluate the requirement of bovine adrenal chromaffin cells for inositol phospholipids in secretion, the effects of neomycin and spermine on secretion and phosphoinositide metabolism were compared. Spermine and neomycin had virtually identical effects on secretion and phosphoinositide levels. Both polyamines 1) partially maintained secretion when added to permeabilized cells in the absence of ATP, 2) had no effect when added to cells in the presence of ATP and 3) inhibited secretion when present with the Ca2+ stimulus. In the absence of ATP the enhancements to secretion due to incubation with either polyamine were associated with sustained levels of the polyphosphoinositides. The ability of spermine and neomycin to maintain secretion and the polyphosphoinositides in the absence of ATP supports the hypothesis that the maintenance of the polyphosphoinositides is necessary for secretion. Neomycin was found to inhibit Ca2+ stimulated production of both inositol bis- and tris-phosphates while spermine was found to selectively inhibit inositol bis-phosphate production and had no effect on Ca2+-stimulated inositol tris-phosphate production in permeabilized cells.