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Two different mechanisms of noradrenaline release during normoxia and simulated ischemia in human cardiac tissue.
J Mol Cell Cardiol. 1995 May; 27(5):1161-72.JM

Abstract

Species-related differences in the mechanisms of noradrenaline release during normoxia and myocardial ischemia emphasize the need for studies on human hearts. Therefore, the mechanisms of noradrenaline release were investigated during normoxia and energy depletion in incubated human atrial tissue and compared to the release characteristics in normoxic and ischemic rat heart. Potential differences of atrial versus ventricular myocardium were assessed by comparing catecholamine release during electrical stimulation and ischemia in isolated rat atrium with release characteristics in the intact perfused heart. The overflow of endogenous noradrenaline and its deaminated metabolite dihydroxyphenylethyleneglycol (DOPEG) were determined by high pressure liquid chromatography and electrochemical detection. During normoxia noradrenaline release was evoked by electrical field stimulation. Stimulation-induced noradrenaline release depended on the extracellular calcium concentration in both species and was almost completely suppressed under calcium-free conditions. The release was significantly inhibited by neuronal (N-type) calcium channel blockers such as omega-conotoxin (100 nmol/l) and cadmium chloride (100 mumol/l), indicating a predominant role of N-type calcium channels in exocytotic noradrenaline release from sympathetic neurons in human and rat heart. Desipramine (100 nmol/l) enhanced the overflow of noradrenaline evoked by electrical stimulation in both species by blocking neuronal catecholamine uptake (uptake1). Myocardial ischemia was caused by interruption of perfusion flow in rat heart and simulated by anoxic and glucose-free incubation in human and rat atrial tissue. Ischemia- and anoxia-induced noradrenaline release in rat heart and human atrial tissue was unaffected by varying extracellular calcium concentrations and occurred even after omission of calcium and addition of EGTA (1 mmol/l). In both species neither omega-conotoxin (100 nmol/l) nor cadmium chloride (100 mumol/l) affected ischemia-induced noradrenaline overflow in both rat heart and atrium as well as in human atrium. In human and rat atrial tissue, blockade of energy metabolism in the presence of oxygen (cyanide model) resulted in a desipramine-sensitive release of noradrenaline, which was accompanied by DOPEG overflow, indicating increased axoplasmic noradrenaline concentration. The data imply a dual mechanism of noradrenaline release in the human heart. During normoxia noradrenaline release is modulated by neuronal calcium influx indicating exocytotic release. Ischemia-induced noradrenaline release, however, is independent of calcium and inhibited by uptake1 blockade suggesting nonexocytotic release mechanism. The characteristics of noradrenaline release in human atrial tissue provide evidence for carrier-mediated release of noradrenaline from sympathetic neurons operative in the ischemic human myocardium.

Authors+Show Affiliations

Department of Medicine I, Technical University, Munich, Germany.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

7473774

Citation

Kurz, T, et al. "Two Different Mechanisms of Noradrenaline Release During Normoxia and Simulated Ischemia in Human Cardiac Tissue." Journal of Molecular and Cellular Cardiology, vol. 27, no. 5, 1995, pp. 1161-72.
Kurz T, Richardt G, Hagl S, et al. Two different mechanisms of noradrenaline release during normoxia and simulated ischemia in human cardiac tissue. J Mol Cell Cardiol. 1995;27(5):1161-72.
Kurz, T., Richardt, G., Hagl, S., Seyfarth, M., & Schömig, A. (1995). Two different mechanisms of noradrenaline release during normoxia and simulated ischemia in human cardiac tissue. Journal of Molecular and Cellular Cardiology, 27(5), 1161-72.
Kurz T, et al. Two Different Mechanisms of Noradrenaline Release During Normoxia and Simulated Ischemia in Human Cardiac Tissue. J Mol Cell Cardiol. 1995;27(5):1161-72. PubMed PMID: 7473774.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Two different mechanisms of noradrenaline release during normoxia and simulated ischemia in human cardiac tissue. AU - Kurz,T, AU - Richardt,G, AU - Hagl,S, AU - Seyfarth,M, AU - Schömig,A, PY - 1995/5/1/pubmed PY - 1995/5/1/medline PY - 1995/5/1/entrez SP - 1161 EP - 72 JF - Journal of molecular and cellular cardiology JO - J Mol Cell Cardiol VL - 27 IS - 5 N2 - Species-related differences in the mechanisms of noradrenaline release during normoxia and myocardial ischemia emphasize the need for studies on human hearts. Therefore, the mechanisms of noradrenaline release were investigated during normoxia and energy depletion in incubated human atrial tissue and compared to the release characteristics in normoxic and ischemic rat heart. Potential differences of atrial versus ventricular myocardium were assessed by comparing catecholamine release during electrical stimulation and ischemia in isolated rat atrium with release characteristics in the intact perfused heart. The overflow of endogenous noradrenaline and its deaminated metabolite dihydroxyphenylethyleneglycol (DOPEG) were determined by high pressure liquid chromatography and electrochemical detection. During normoxia noradrenaline release was evoked by electrical field stimulation. Stimulation-induced noradrenaline release depended on the extracellular calcium concentration in both species and was almost completely suppressed under calcium-free conditions. The release was significantly inhibited by neuronal (N-type) calcium channel blockers such as omega-conotoxin (100 nmol/l) and cadmium chloride (100 mumol/l), indicating a predominant role of N-type calcium channels in exocytotic noradrenaline release from sympathetic neurons in human and rat heart. Desipramine (100 nmol/l) enhanced the overflow of noradrenaline evoked by electrical stimulation in both species by blocking neuronal catecholamine uptake (uptake1). Myocardial ischemia was caused by interruption of perfusion flow in rat heart and simulated by anoxic and glucose-free incubation in human and rat atrial tissue. Ischemia- and anoxia-induced noradrenaline release in rat heart and human atrial tissue was unaffected by varying extracellular calcium concentrations and occurred even after omission of calcium and addition of EGTA (1 mmol/l). In both species neither omega-conotoxin (100 nmol/l) nor cadmium chloride (100 mumol/l) affected ischemia-induced noradrenaline overflow in both rat heart and atrium as well as in human atrium. In human and rat atrial tissue, blockade of energy metabolism in the presence of oxygen (cyanide model) resulted in a desipramine-sensitive release of noradrenaline, which was accompanied by DOPEG overflow, indicating increased axoplasmic noradrenaline concentration. The data imply a dual mechanism of noradrenaline release in the human heart. During normoxia noradrenaline release is modulated by neuronal calcium influx indicating exocytotic release. Ischemia-induced noradrenaline release, however, is independent of calcium and inhibited by uptake1 blockade suggesting nonexocytotic release mechanism. The characteristics of noradrenaline release in human atrial tissue provide evidence for carrier-mediated release of noradrenaline from sympathetic neurons operative in the ischemic human myocardium. SN - 0022-2828 UR - https://www.unboundmedicine.com/medline/citation/7473774/Two_different_mechanisms_of_noradrenaline_release_during_normoxia_and_simulated_ischemia_in_human_cardiac_tissue_ L2 - https://linkinghub.elsevier.com/retrieve/pii/0022-2828(95)90052-7 DB - PRIME DP - Unbound Medicine ER -