Probable participation of phospholipase A2 reaction in the process of fertilization-induced activation of sea urchin eggs.
In sea urchin eggs activated by sperm, A23187 or melittin, BPB (4-bromophenacyl bromide, a phospholipase A2 inhibitor) blocked fertilization envelope formation and transient CN(-)-insensitive respiration in a concentration-dependent manner. BPB had virtually no effect on the increase in [Ca2+]i (cytosolic Ca2+ level), the activity of phosphorylase a and the rate of protein synthesis, as well as acid production and augmentation of CN(-)-sensitive respiration. BPB also inhibited fertilization envelope formation and augmentation of CN(-)-insensitive respiration induced by melittin. Melittin, known to be an activator of phospholipase A2, induced the envelope formation, acid production, augmentation of CN(-)-insensitive and sensitive respiration, but did not cause any increase in [Ca2+]i, the phosphorylase a activity and the rate of protein synthesis. An activation of phospholipase A2 induced by Ca2+ or melittin seems to result in cortical vesicle discharge and production of fatty acids, which are to be utilized in CN(-)-insensitive lipid peroxidase reactions. Activation of other examined cell functions in eggs activated by sperm or A23187, probably results from Ca(2+)-triggered sequential reactions other than Ca(2+)-caused activation of phospholipase A2.
Kamata
Y
Y
Department of Biology, School of Education, Waseda University, Tokyo, Japan.
Mita
M
M
Fujiwara
A
A
Tojo
T
T
Takano
J
J
Ide
A
A
Yasumasu
I
I
D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003486:Cyanides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005306:Fertilization / Q000187:drug effects / Q000502:physiology*; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008555:Melitten / Q000494:pharmacology; D010063:Ovum / Q000187:drug effects / Q000502:physiology*; D010101:Oxygen Consumption / Q000187:drug effects; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D012617:Sea Urchins / Q000502:physiology*
D000098:Acetophenones; D003486:Cyanides; D004791:Enzyme Inhibitors; D007476:Ionophores; D008555:Melitten; D000001:Calcimycin; D010741:Phospholipases A; D054467:Phospholipases A2; C006821:4-bromophenacyl bromide; D002118:Calcium