U73122 blocked the cGMP-induced calcium release in sea urchin eggs.
U73122, a phospholipase C inhibitor, dose dependently blocks the cGMP-induced Ca2+ release in sea urchin eggs and homogenates. U73122 inhibition was prevented by cotreatment with dithiothreitol (DTT), but DTT is ineffective when eggs or homogenates were pretreated with U73122. U73122 action is different from the other sulfhydryl reagents, thimerosal and N-ethylmaleimide, which cause Ca2+ release in egg homogenates at high concentration, but at lower concentration have no significant effect on cGMP-induced Ca2+ release. Histone, a reported NAD glycohydrolase (NADase) activator, was found to induce Ca2+ release in egg homogenates via the same pathway as the cGMP response, since histone-induced Ca2+ release is blocked by Rp-8-pCPT-cGMPS, a cGMP-dependent protein kinase (PKG) inhibitor, and nicotinamide, a NADase inhibitor. Histone-induced Ca2+ release is similarly blocked by U73122. The aminosteroid U73122 does not inhibit cADPR-induced Ca2+ release, which is significantly reduced by PKG inhibitors. Furthermore, U73122 has no significant effect on phorbol 12-myristate 13-acetate induced-cytoplasmic alkalinization in intact eggs, which depends on protein kinase C activity. These results suggest that U73122 does not act as a general serine-threonine protein kinase inhibitor, and the aminosteroid inhibition of the cGMP-induced Ca2+ release may interfere with ADP ribosyl cyclase activity.
Department of Zoology and Genetics, Iowa State University, Ames 50011-3223, USA.
S J
SJ
Lee
P J
PJ
Madden
S S
SS
Shen
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D036563:Cyclic ADP-Ribose; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology*; D006657:Histones / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D009244:NAD+ Nucleosidase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009536:Niacinamide / Q000494:pharmacology; D010063:Ovum; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011760:Pyrrolidinones / Q000494:pharmacology*; D012617:Sea Urchins; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors*
C090860:8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphorothioate; D004791:Enzyme Inhibitors; D004963:Estrenes; D006657:Histones; D007546:Isoquinolines; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D013439:Sulfhydryl Reagents; D013873:Thionucleotides; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D036563:Cyclic ADP-Ribose; D000246:Adenosine Diphosphate Ribose; D013849:Thimerosal; D009536:Niacinamide; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; D017869:Cyclic GMP-Dependent Protein Kinases; D011493:Protein Kinase C; D010738:Type C Phospholipases; D009244:NAD+ Nucleosidase; D006152:Cyclic GMP; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D004229:Dithiothreitol