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| Author(s): |
Felipe Fernandes Jacintho
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas |
| Defense date: | 2023-12-01 |
| Examining board members: |
Gilberto De Nucci;
Gláucia Coelho de Melo;
Juliana Signori Baracat Zeferino;
Natalícia de Jesus Antunes;
Gustavo Duarte Mendes
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| Advisor: | Gilberto De Nucci |
| Abstract | |
The endothelium is an organ capable of regulating vascular tone through the release of relaxing agents such as nitric oxide and prostacyclin, or contractile agents, such as endothelins and angiotensin. The current physiological concept proposes that such regulation can also occur through the release of catecholamines of exclusively neural origin, but isolated tissues of reptiles with endothelium constitute a source of catecholamines, since aortic contraction induced by electric field stimulation is abolished by adrenergic antagonists and by removing the endothelium. Immunohistochemistry identified the presence of the enzyme tyrosine hydroxylase in the endothelium of human tissue, snakes and Chelonoidis carbonaria. This study aimed to identify the mediator(s) responsible for the contractions induced by electric field stimulation (EFS) of the aortic rings of Chelonoidis carbonaria and understand their physiological function. The aortic rings were mounted in an isolated organ bath with oxygenated and heated Krebs-Henseleit solution. Contractions were assessed in the presence and absence of L-NAME, tetrodotoxin, phentolamine, phenoxybenzamine, Prazosin, idazoxan, atropine, D-tubocurarine, or indomethacin. EFS-induced contraction was also performed in rings lacking endothelium. EFS-induced contraction was investigated by sandwich assay. EFS at 16 Hz contracted Chelonoidis's aorta, which was nearly abolished by removal of the endothelium. The addition of L-NAME increased the EFS response. In aortic rings treated with L-NAME, tetrodotoxin did not alter the EFS response. Indomethacin, Prazosin, idazoxan atropine and d-tubucurarine also did not affect the EFS response. Phentolamine at 10 ?M did not alter the contraction induced by EFS, however, at 100 µM it reduced it. Phenoxybenzamine at 1 µM reduced the EFS response by 76% and at 10 µM by 90%. Immunohistochemistry identified tyrosine hydroxylase in the endothelium and brain, while the S100 protein was found only in the brain. The concentrations of dopamine, norepinephrine and adrenaline were analyzed by liquid chromatography coupled to tandem mass spectrometry. The contractions caused by dopamine and EFS were performed in the absence and presence of the nitric oxide (NO) synthesis inhibitor L-NAME, the NO-sensitive guanylyl cyclase inhibitor ODQ, the D1-type receptor antagonist SCH-23390, the D1-type receptor antagonist D2 antagonists risperidone, quetiapine, haloperidol and the tyrosine hydroxylase inhibitors salsolinol and 3-iodo-L-tyrosine. Basal concentrations of dopamine, norepinephrine and adrenaline were detected in Krebs solution containing the aortic rings. Catecholamine concentrations were significantly reduced in aortic rings without endothelium. L-NAME and ODQ significantly potentiated dopamine-induced contractions. D2-like receptor antagonists inhibited EFS-induced contractions of L-NAME-treated aortic rings, whereas SCH 23390 had no effect. Similar results were observed in dopamine-induced contractions in aortic rings treated with L-NAME. These results indicate that catecholamines released by the endothelium regulate EFS-induced contractions. This may constitute a suitable mechanism by which reptiles modulate the distribution of blood flow in specific organs (AU) | |
| FAPESP's process: | 18/24971-9 - Physiological relevance of catecholamines produced by the endothelium |
| Grantee: | Felipe Fernandes Jacintho |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |