Substance P action on inositol phospholipids in rat adrenal medulla slices

The effect of SP (1.10(-6) M) on the 32P incorporation into inositol phospholipids from rat adrenal medulla slices has been examined. After 20 s, a decreased 32P incorporation into all inositol phospholipids was found (most expressed for phosphatidyl-inositol-4,5-bisphosphate) without changes in phosphatidylcholine/phospatidylserine fraction. During 5 min exposure to SP the 32P incorporation into phosphatidylinositol-4,5-bisphosphate returned up to the control level, whereas that into phosphatidylcholine/phosphatidylserine fraction strongly decreased. A within-one-sample comparison of the radioactivity of each phospholipid against that in the phosphatidylcholine/phosphatidylserine fraction reveals a "phosphatidylinositol effect". A possible regulation mechanism of catecholamine secretion by SP in relation to changes in inositol phospholipids is discussed.