ARACHIDONIC-ACID, PROTEIN-KINASE-C ACTIVATORS AND BUD FORMATION IN HYDRA-VULGARIS

1. The effect of the protein kinase C (PKC) activators verrucosin B (VB), 1,2-sn-dioctanoylglycerol (diC8) and phorbol-12-myristate-13-acetate (PMA), of arachidonic acid (AA) and of substances interfering with its release, re-uptake and metabolism was studied in Hydra vulgaris. 2. All PKC activators potently inhibited bud formation, VB and PMA being 10,000 x more potent than diC8. VB effect was maximal already after 10 min incubation with hydra and persisted at 24 hr incubations. 3. AA and substances inhibiting its re-uptake from cell membrane or its metabolism also inhibited bud formation, whereas oleyl-oxyethyl-phosphorylcholine (OOPC), an inhibitor of phospholipase A2, potently induced bud formation. 4. The findings described herein suggest a role for both PKC activation and AA in the inhibition of bud formation in H. vulgaris.