title: cGMP inhibits IP3-induced Ca2+ release in intact rat megakaryocytes via cGMP- and cAMP-dependent protein kinases.
abstract: 1. Inhibition of inositol 1,4,5-trisphosphate (IP3) receptor-mediated Ca2+ release by cGMP was examined in intact rat megakaryocytes, by using a combination of single cell fluorescence microscopy to monitor intracellular free calcium ([Ca2+]i) and flash photolysis of caged second messengers. 2. Sodium nitroprusside (SNP), a nitric oxide (NO) donor, and the hydrolysis-resistant cGMP analogue 8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphate (pCPT-cGMP) inhibited Ca2+ release induced by photolysis of caged IP3. Neither of them affected the rate of Ca2+ removal from the cytoplasm following photolysis of caged Ca2+. 3. Photolysis of the caged NO donor 3-morpholinosydnonimine (SIN-1) during agonist-induced [Ca2+]i oscillations inhibited Ca2+ release without affecting the rate of Ca2+ uptake and/or extrusion. 4. We conclude that the inhibition of IP3-induced Ca2+ release is the principal mechanism of NO-cGMP-dependent inhibition of [Ca2+]i mobilization. 5. IPG, a specific peptide inhibitor of cGMP-dependent protein kinase (cGMP-PK), blocked the inhibitory effect of pCPT-cGMP, indicating that the inhibition of IP3-induced Ca2+ release by pCPT-cGMP is mediated by cGMP-PK. However, the simultaneous application of both IPG and IP20, a specific peptide inhibitor of cAMP-dependent protein kinase (cAMP-PK), was required to block the inhibitory effect of SNP. These data strongly suggest that NO-cGMP-dependent inhibition of [Ca2+]i mobilization is mediated via the activation of both cGMP-PK and cAMP-PK.
authors.affiliation: Department of Physiology, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: S
authors.initials: S
authors.lastname: Tertyshnikova
authors.forename: X
authors.initials: X
authors.lastname: Yan
authors.forename: A
authors.initials: A
authors.lastname: Fein
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D002118:Calcium / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007700:Kinetics; D008533:Megakaryocytes / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D010782:Photolysis; D051381:Rats; D017208:Rats, Wistar; D015290:Second Messenger Systems; D013873:Thionucleotides / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D013873:Thionucleotides; D009599:Nitroprusside; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; C002385:linsidomine; D015544:Inositol 1,4,5-Trisphosphate; D008981:Molsidomine; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP; D002118:Calcium