title: Negative functional effects of cyclic GMP are altered by cyclic AMP phosphodiesterases in rabbit cardiac myocytes.
abstract: In this study, we tested the hypothesis that the negative functional effects of cyclic GMP on cardiac myocytes would be affected by the actions of cyclic GMP on cyclic AMP phosphodiesterases. Ventricular myocytes from eight rabbits were used to determine the functional and cyclic AMP changes caused by 10(-7), 10(-6), 10(-5) M 8-Bromo-cGMP alone and after the administration of 10(-6) M milrinone (cyclic GMP-inhibited cyclic AMP phosphodiesterase inhibitor) or 10(-6) M erythro-9-(2-Hydroxy-3-3-nonyl)adenine (EHNA, cyclic GMP-stimulated cyclic AMP phosphodiesterase inhibitor). 8-Br-cGMP dose-dependently reduced %shortening by 35+/-4% of baseline at 10(-5) M. This effect was significantly blunted by EHNA at all doses. The maximum rate of shortening was reduced by 31+/-3% by 10(-5) M 8-Br-cGMP. This effect of 8-Br-cGMP was significantly enhanced (42+/-4%) in the milrinone group. A similar pattern was observed in the maximum rate of relaxation data. Cyclic AMP levels were significantly increased from a baseline level of 4.0+/-0.8 pmol/10(5) myocytes by milrinone (+60%), EHNA (+61%) and 8-Br-cGMP (+47%). The combination of EHNA plus 8-Br-cGMP increased cyclic AMP levels significantly more that the combination of milrinone plus 8-Br-cGMP. Exogenous cyclic GMP reduces myocyte function, while raising cyclic AMP possibly through cyclic GMP-inhibited cyclic AMP phosphodiesterase effects. Blocking cyclic GMP-inhibited cyclic AMP phosphodiesterase enhances the functional effects cyclic GMP, while blocking cyclic GMP-stimulated cyclic AMP phosphodiesterase reduced these effects. The study demonstrated a functional interaction between cyclic GMP and cyclic AMP related to the cyclic GMP affected cyclic AMP phosphodiesterases.
authors.affiliation: Heart and Brain Circulation Laboratory, Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854-5635, USA. hweiss@umdnj.edu
authors.forename: Harvey R
authors.initials: HR
authors.lastname: Weiss
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lazar
authors.forename: Kusum
authors.initials: K
authors.lastname: Punjabi
authors.forename: James
authors.initials: J
authors.lastname: Tse
authors.forename: Peter M
authors.initials: PM
authors.lastname: Scholz
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D048429:Cell Size / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D020105:Milrinone / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011817:Rabbits; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D010726:Phosphodiesterase Inhibitors; D013873:Thionucleotides; C083763:8-bromoguanosino-3',5'-cyclic monophosphorothioate; C010192:9-(2-hydroxy-3-nonyl)adenine; D000242:Cyclic AMP; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D006152:Cyclic GMP; D000225:Adenine; D020105:Milrinone