The fucose-sulfate glycoconjugate that induces an acrosome reaction in spermatozoa stimulates inositol 1,4,5-trisphosphate accumulation.
The hydrolysis of phosphatidylinositol may generate multiple second messengers, including inositol phosphates, 1,2-diacylglycerol, arachidonic acid, and phosphatidic acid. Here, we describe for the first time in spermatozoa that accumulation of one of these potential second messengers, inositol 1,4,5-trisphosphate (1,4,5-IP3), can be stimulated by the fucose-sulfate glycoconjugate (FSG) that induces an acrosome reaction. Sea urchin spermatozoa were labeled with myo-[3H]inositol and incubated with FSG. The amount of [3H]1,4,5-IP3 obtained from FSG-treated cells was up to 10 times that from untreated cells. Increases in the amount of [3H]1,4,5-IP3 were detected within 30 s after addition of FSG (2.5-fold) and were highest at 2 min after addition. Previously, it was shown that FSG induces Ca2+-dependent increases in cyclic AMP concentrations (Kopf, G. S., and Garbers, D. L. (1980) Biol. Reprod. 22, 1118-1126). Increases in [3H]1,4,5-IP3 accumulation caused by FSG were also dependent on extracellular Ca2+. The Ca2+ channel blockers, verapamil and nifedipine, inhibited increases in both [3H]1,4,5-IP3 and cyclic AMP, and the addition of concentrations of extracellular Ca2+ higher than 9.6 mM could reduce the inhibition. When spermatozoa were incubated in Ca2+-free seawater, FSG-induced increases in [3H]1,4,5-IP3 and cyclic AMP concentrations were blocked; addition of extracellular Ca2+ restored the responses. Other treatments that result in the induction of an acrosome reaction, including the addition of monovalent cation H+ exchangers, nigericin and gramicidin S, and incubation in seawater at alkaline pH (pH 8.8), also stimulated accumulation of [3H]1,4,5-IP3 and cyclic AMP.
D000177:Acrosome / Q000187:drug effects*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005643:Fucose / Q000494:pharmacology*; D006096:Gramicidin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D009550:Nigericin / Q000494:pharmacology; D012617:Sea Urchins; D013094:Spermatozoa / Q000187:drug effects* / Q000378:metabolism*; D013403:Sugar Phosphates / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
D007295:Inositol Phosphates; D013403:Sugar Phosphates; D006096:Gramicidin; D005643:Fucose; D015544:Inositol 1,4,5-Trisphosphate; D014700:Verapamil; D000242:Cyclic AMP; D009543:Nifedipine; D009550:Nigericin; D002118:Calcium