Potentiation of sympathetic neurotransmission in bovine isolated irides by isoprostanes
| Autor: | Lydia C. Harris, Sunny E. Ohia, S. Olubusayo Awe, Angela M. LeDay, Catherine A. Opere |
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| Rok vydání: | 2001 |
| Předmět: |
Agonist
medicine.medical_specialty Sympathetic Nervous System medicine.drug_class Thromboxane Stereochemistry Receptors Thromboxane Iris Isoprostanes Neurotransmission Dinoprost Synaptic Transmission Biochemistry Dinoprostone Norepinephrine chemistry.chemical_compound Isomerism Internal medicine medicine Animals Vasoconstrictor Agents Receptor F2-Isoprostanes biology Chemistry Antagonist Hydrogen Peroxide General Medicine Bridged Bicyclo Compounds Heterocyclic Electric Stimulation Hydrazines Endocrinology 15-Hydroxy-11 alpha 9 alpha-(epoxymethano)prosta-5 13-dienoic Acid Fatty Acids Unsaturated biology.protein Cattle Arachidonic acid Thromboxane-A Synthase Cyclooxygenase |
| Zdroj: | Free Radical Research. 35:257-264 |
| ISSN: | 1029-2470 1071-5762 |
| DOI: | 10.1080/10715760100300791 |
| Popis: | Isoprostanes (IsoP) are formed by free radical catalyzed peroxidation of arachidonic acid independent of the cyclooxygenase enzyme. In the present study, we examined the effect of IsoP on norepinephrine (NE) release from the bovine isolated iris. Furthermore, we studied the role of IsoP's in hydrogen peroxide (H2O2)-induced enhancement of NE release from this tissue. Isolated bovine irides were prepared for studies of [3H]NE release using the superfusion method. Release of [3H]NE was induced via electrical field stimulation. Both 8-iso-prostaglandin E2 (E2-IsoP) and 8-iso-prostaglandin F2 alpha (F2-IsoP) produced a concentration-related enhancement of field-stimulated [3H]NE release from isolated bovine irides, an effect that was mimicked by the thromboxane (Tx) receptor agonist, U46619 and by H2O2. The Tx-receptor antagonist, SQ 29548 inhibited responses to E2-IsoP (10 microM) with an IC50 of 370 +/- 50 nM. SQ 29548 (10 microM) also blocked the enhancement of electrically-evoked [3H]NE release induced by U46619 (10 microM) but not that caused by H2O2 (300 microM). The Tx synthetase inhibitor, carboxyheptylimidazole (10 microM) prevented the stimulatory effect of E2-IsoP on evoked [3H]NE release without affecting responses induced by H2O2. We conclude that IsoP's can enhance sympathetic neurotransmission in the bovine isolated iris, an effect that can be blocked by a Tx-receptor antagonist. Furthermore, endogenously produced Tx's mediate the stimulatory effect of IsoP's on NE release. However, endogenously generated IsoP's or Tx's are not involved in H2O2-induced potentiation of sympathetic neurotransmission. |
| Databáze: | OpenAIRE |
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