. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLYSPERMY BLOCKS 295 Arachidonic acid cascade Changes in phospholipid metaboHsm occur in sea urchin eggs during fertilization (Schmell and Lennarz, 1974; Barber and Mead, 1975; Byrd, 1975; Kozhina et ai, 1978; Barber, 1979; Turner et ai, 1983). Membrane fusion between secretory granules and the plasma membrane is promoted by the action of a calcium-activated phos- pholipase A2 in both somatic secretory cells (Laychock and Putney, 1982; Rubin, 1982) as well as sea urchin eggs (Ferguson and Shen, 1984) and sperm (Conway and M
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLYSPERMY BLOCKS 295 Arachidonic acid cascade Changes in phospholipid metaboHsm occur in sea urchin eggs during fertilization (Schmell and Lennarz, 1974; Barber and Mead, 1975; Byrd, 1975; Kozhina et ai, 1978; Barber, 1979; Turner et ai, 1983). Membrane fusion between secretory granules and the plasma membrane is promoted by the action of a calcium-activated phos- pholipase A2 in both somatic secretory cells (Laychock and Putney, 1982; Rubin, 1982) as well as sea urchin eggs (Ferguson and Shen, 1984) and sperm (Conway and Metz, 1976; SeGall and Lennarz, 1981). Phospholipase A2 releases a free fatty acid (usually arachidonic acid) and lysophosphoglycerides from membrane phosphoglycer- ides (Fig. 14). These substances may be re-incorporated into membrane phospholipids via reacylation reactions in sea urchin eggs during fertilization (Schmell and Lennarz, 1974; Turner et ai, 1983) or in secreting somatic cells (Laychock and Putney. 1982; Rubin, 1982). Lysophosphoglycerides can initiate exocytosis by promoting membrane fusion (Lucy, 1970; Laychock and Putney, 1982). Free arachidonic acid can be oxidized by two major pathways (Kuehl and Egan, 1980). The cyclooxygenase pathway leads to the production of prostaglandins and thromboxanes. Non-steroidal anti-inflam- matory drugs (NSAID) act by inhibiting cyclooxygenase (Flower, 1974; Kuehl and Egan, 1980). The lipoxygenase pathway leads to the production of the leukotrienes and hydroxy fatty acids (HETE's). Cells may contain different lipoxygenases which oxidize the carbon atom at positions 5, 11, 12, or 15 of arachidonic acid (Nelson et ai, 1982; Samuelsson, 1983). Leukotrienes are products of the 5-lipoxygenase pathway. The slow reacting substance of anaphylaxis (SRS-A) consists of leukotrienes LTC4, MEMBRANE PHOSPHOLIPIDS PHOSPHOLIPASE A2 CA-^+ACTIVATED QUINACRINE INHIBITS REACYLATION ARACHIDONIC ACID+LYSOPHO SPHOGYICERIDES ?REACVIATION CYCLOOXYGENASE N
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