title: Simultaneous measurement of intracellular nitric oxide and free calcium levels in chordate eggs demonstrates that nitric oxide has no role at fertilization.
abstract: At fertilization in sea urchin, the free radical nitric oxide (NO) has recently been suggested to cause the intracellular Ca(2+) rise responsible for egg activation. The authors suggested that NO could be a universal activator of eggs and the present study was set up to test this hypothesis. Intracellular NO and Ca(2+) levels were monitored simultaneously in eggs of the mouse or the urochordate ascidian Ascidiella aspersa. Eggs were either fertilized or sperm extracts microinjected. Sperm-induced Ca(2+) rises were not associated with any global, or local, change in intracellular NO, although we were able to detect NO produced by the addition of a NO donor. Furthermore, the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester had no effect on sperm-induced Ca(2+) release but did block completely ionomycin-induced NO synthase activation. Therefore, we suggest that the current data provide evidence that NO has no role in the fertilization of these two chordate eggs.
authors.affiliation: Department of Physiological Sciences, The Medical School, Framlington Place, The University of Newcastle, Newcastle, NE2 4HH, England, UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Hyslop
authors.forename: M
authors.initials: M
authors.lastname: Carroll
authors.forename: V L
authors.initials: VL
authors.lastname: Nixon
authors.forename: A
authors.initials: A
authors.lastname: McDougall
authors.forename: K T
authors.initials: KT
authors.lastname: Jones
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002816:Chordata, Nonvertebrate / Q000502:physiology*; D004789:Enzyme Activation; D005260:Female; D005306:Fertilization / Q000502:physiology*; D005452:Fluoresceins; D016257:Fura-2; D008297:Male; D051379:Mice; D008856:Microscopy, Fluorescence; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D010063:Ovum / Q000502:physiology*; D012617:Sea Urchins; D013552:Swine; D014561:Urochordata; D014714:Vertebrates / Q000502:physiology*
chemical_list: C112456:4,5-diamino-2-(3,6-dihydroxy-9H-xanthen-9-yl)benzoic acid; D005452:Fluoresceins; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D002118:Calcium; D016257:Fura-2