h-89 and olprinone

Olprinone, an inhibitor of cyclic nucleotide phosphodiesterase III, inhibited an increase in intracellular Ca(2+) concentrations for acutely dissociated rat hippocampal pyramidal neurons induced by extracellular high K(+) (35 mM) depolarization. Olprinone (100 microM) significantly reduced spontaneous glutamate release from rat hippocampal slices. Furthermore, olprinone significantly decreased the rate of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated miniature excitatory postsynaptic currents (AMPA-mEPSCs) monitored from CA1 pyramidal neurons of rat hippocampal slices, and the effect was blocked by KT5823, an inhibitor of protein kinase G (PKG), but not by H-89, an inhibitor of protein kinase A (PKA). In the PKA assay using PC-12 cells, olprinone did not activate PKA. Taken together, the results of the present study show that olprinone attenuates intracellular Ca(2+) rise through voltage-sensitive Ca(2+) channels and inhibits presynaptic glutamate release via a cGMP/PKG pathway.

Topics: Animals; Calcium; Carbazoles; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Excitatory Postsynaptic Potentials; Glutamic Acid; Hippocampus; Imidazoles; In Vitro Techniques; Isoquinolines; Male; Membrane Potentials; Phosphodiesterase 3 Inhibitors; Phosphodiesterase Inhibitors; Potassium; Protein Kinase Inhibitors; Pyramidal Cells; Pyridones; Rats; Rats, Wistar; Receptors, AMPA; Signal Transduction; Sulfonamides

Phosphodiesterase III inhibitors (PDEIII-Is) improve the hemodynamic status of heart failure via inotropic/vasodilatory effects attributable to the increase in intracellular cAMP level. Direct cardioprotection by PDEIII-Is and its underlying mechanisms, however, have not been identified. We tested the infarct size-limiting effect of PDEIII-Is and the roles of cAMP, protein kinase (PK) A, PKC, and mitogen-activated protein kinase (MAPK) families in open-chest dogs. Methods and Results-- Milrinone, olprinone (PDEIII-Is), or dibutyryl-cAMP (db-cAMP) was injected intravenously 30 minutes before 90-minute ischemia, followed by 6 hours of reperfusion. Olprinone was also examined with an intracoronary cotreatment with a PKA inhibitor (H89), a PKC inhibitor (GF109203X), an extracellular signal-regulated kinase kinase (MEK) inhibitor (PD98059), or a p38 MAPK inhibitor (SB203580) throughout the preischemic period. Either PDEIII-Is or db-cAMP caused substantial hemodynamic changes, which returned to control levels in 30 minutes. Collateral flow and percent risk area were identical for all groups. Both PDEIII-Is and db-cAMP increased myocardial p38 MAPK activity during the preischemic period, which was blocked by H89, but not by GF109203X. Both PDEIII-Is and db-cAMP reduced infarct size (19.1+/-4.1%, 17.5+/-3.3%, and 20.3+/-4.8%, respectively, versus 36.1+/-6.2% control, P<0.05 each). Furthermore, the effect of olprinone was blunted by either H89 (35.5+/-6.4%) or SB203580 (32.6+/-5.9%), but not by GF109203X or PD98059. H89, GF109203X, PD98059, or SB203580 alone did not influence infarct size.. Pretreatment with PDEIII-Is has cardioprotective effects via cAMP-, PKA-, and p38 MAPK-dependent but PKC-independent mechanisms in canine hearts.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Blood Flow Velocity; Bucladesine; Calcium-Calmodulin-Dependent Protein Kinases; Cardiovascular Agents; Cyclic AMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 3; Dogs; Enzyme Inhibitors; Flavonoids; Hemodynamics; Imidazoles; Indoles; Isoquinolines; Maleimides; Milrinone; Mitogen-Activated Protein Kinases; Myocardial Infarction; p38 Mitogen-Activated Protein Kinases; Phosphodiesterase Inhibitors; Protein Kinase C; Pyridines; Pyridones; Sulfonamides; Ventricular Fibrillation