phosphoramidon and chelerythrine

This study tested the hypothesis that vasospasm due to subarachnoid hemorrhage involves the functional upregulation of protein kinase C. Spasm of the rabbit basilar artery was achieved using a double hemorrhage model, which we previously demonstrated was endothelin-1 dependent. In situ effects of agents were determined by direct measurement of vessel diameter following their suffusion in a cranial window. Chelerythrine, a protein kinase C inhibitor, relaxed the spasm. However, relaxations to chelerythrine were not significantly greater in endothelin-1 constricted spastic vessels initially relaxed with the endothelin converting enzyme inhibitor, phosphoramidon, as compared to endothelin-1 constricted control vessels. These results suggest that subarachnoid hemorrhage induced vasospasm does not involve functional upregulation of protein kinase C.

Topics: Alkaloids; Animals; Basilar Artery; Benzophenanthridines; Endothelin-1; Enzyme Inhibitors; Glycopeptides; Male; Phenanthridines; Protease Inhibitors; Protein Kinase C; Rabbits; Subarachnoid Hemorrhage; Up-Regulation; Vasoconstriction; Vasospasm, Intracranial

Transient ischemia has been shown to impair endothelium-dependent, but not endothelium-independent, coronary vasodilation, indicating selective endothelial dysfunction. Here a hypothesis was tested that agonist mediated activation of protein kinase C (PKC) and the related overproduction of the oxidative species contribute to the mechanism of the endothelial dysfunction. Perfused guinea-pig hearts were subjected either to 30 min global ischemia/30 min reperfusion or to 30 min aerobic perfusion with a PKC activator, phorbol ester (1 n M, PMA). Coronary flow responses to a bolus of acetylcholine (ACh) and sodium nitroprusside (SNP) were used as measures of endothelium-dependent and endothelium-independent vascular function, respectively. Salicylate hydroxylation was used as the assay for the myocardial hydroxyl radical (.OH) formation. Both ischemia/reperfusion and PMA impaired the ACh response and augmented the myocardial.OH production. The effect of ischemia/reperfusion on the ACh response: (i) was fully prevented by a PKC inhibitor, chelerythrine (2microM) and a mixed endothelin blocker, bosentan (20microM); (ii) was partially prevented by an endothelin converting-enzyme inhibitor, phosphoramidon (40microM), and superoxide dismutase (150-500 U/ml, SOD) and (iii) was affected neither by catalase (600 U/ml) nor by losartan (20microM) and captopril (250microM), nor by prazosin (10microM). SOD, but not bosentan, partially prevented the effect of PMA on the ACh response. None of the interventions studied affected the SNP response. The reperfusion-induced.OH release was attenuated by chelerythrine and bosentan, was not affected by prazosin and was increased by SOD. These results implicate the following sequence of events in the mechanism of the post-ischemic endothelial dysfunction: ischemia/reperfusion, endothelin-induced PKC activation, increased production of superoxide and/or some of its toxic metabolite, damage to the endothelium and endothelial dysfunction. The results argue against the contribution of angiotensin II, adrenergicalpha(1)-receptors and kinins in the mechanism of the post-ischemic endothelial dysfunction in guinea-pig hearts.

Topics: Acetylcholine; Adrenergic alpha-Antagonists; Alkaloids; Angiotensin-Converting Enzyme Inhibitors; Animals; Anti-Arrhythmia Agents; Aspartic Acid Endopeptidases; Benzophenanthridines; Bosentan; Captopril; Catalase; Coronary Vessels; Endothelin-Converting Enzymes; Endothelins; Endothelium, Vascular; Enzyme Activation; Enzyme Inhibitors; Female; Free Radicals; Glycopeptides; Guinea Pigs; Heart; Losartan; Male; Metalloendopeptidases; Muscle Proteins; Myocardial Ischemia; Myocardial Reperfusion; Myocardium; Nitroprusside; Oxidative Stress; Phenanthridines; Prazosin; Protein Kinase C; Reactive Oxygen Species; Sulfonamides; Superoxide Dismutase; Tetradecanoylphorbol Acetate; Vasodilator Agents

Previous results from our laboratory have suggested that morphine can attenuate neutrophil activation in patients with acute myocardial infarction. To elucidate if morphine preconditioning (PC) has the same effects via activation of neutrophil endopeptidase 24.11 (NEP), we measured serum levels of intercellular adhesion molecule-1 (ICAM-1), gp100MEL14 and NEP in adult Wistar rats subjected to ten different protocols (n = 10 for each) at baseline, immediately after and 2 h after morphine PC. All groups were subjected to 30 min of occlusion and 2 h of reperfusion. Similarly, morphine-induced PC was elicited by 3-min drug infusions (100 micrograms/kg) interspersed with 5-min drug-free periods before the prolonged 30-min occlusion. Infarct size (IS), as a percentage of the area at risk (AAR), was determined by triphenyltetrazolium staining. Pretreatment with morphine increased NEP activities (9.86 +/- 1.98 vs. 5.12 +/- 1.10 nmol/mg protein in control group; p < 0.001). Naloxone (mu-opioid receptor antagonist) (4.82 +/- 1.02 nmol/mg protein) and phosphoramidon (NEP inhibitor) (4.66 +/- 1.00 nmol/mg protein) inhibited morphine-activated NEP, whereas glibenclamide (ATP-sensitive potassium channel antagonist) and chelerythrine (protein kinase C inhibitor) had no effects. The ICAM-1 and gp100MEL14 of the third sampling were lowest for those with morphine PC (280 +/- 30 ng/ml and 2.2 +/- 0.7 micrograms/ml; p < 0.001), but naloxone (372 +/- 38 ng/ml and 3.8 +/- 0.9 micrograms/ml) and phosphoramidon (382 +/- 40 ng/ml and 4.2 +/- 1.1 micrograms/ml) abolished the above phenomenon. IS/AAR were definitely lowest for those with morphine PC (24 +/- 7%; p < 0.05). Morphine preconditioning increases NEP activities to attenuate shedding of gp100MEL14 and to ICAM-1 and, thus, provides myocardial protection.

Topics: Alkaloids; Animals; Benzophenanthridines; Glyburide; Glycopeptides; Hypoglycemic Agents; Intercellular Adhesion Molecule-1; Ischemic Preconditioning, Myocardial; L-Selectin; Male; Morphine; Myocardial Infarction; Naloxone; Narcotic Antagonists; Narcotics; Neprilysin; Neutrophil Activation; Neutrophils; Phenanthridines; Potassium Channel Blockers; Protease Inhibitors; Protein Kinase C; Random Allocation; Rats; Rats, Wistar