Catecholamine receptor in the seawater eel intestine |
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Authors: | M Ando E Omura |
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Institution: | (1) Laboratory of Physiology, Faculty of Integrated Arts and Sciences, Hiroshima University, 730 Hiroshima, Japan |
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Abstract: | Dose-response relationships of catecholamines on seawater eel intestinal ion transport were obtained; the potency order being (-)adrenalin>(-)noradrenalin=clonidine>(±)noradrenalin (racemic form of noradrenalin)>(-)phenylephrine>dopamine>(±)isoproterenol, indicating that 2 are more potent than 1- or -agonists. In addition, the effects of adrenalin were completely blocked by yohimbine ( 2-antagonists) but not by prazosin ( 1-antagonists) or propranolol ( -antagonist). These results indicate the existence of an 2-receptor in the seawater eel intestine. Adrenalin may activate the 2-receptor physiologically, since adrenalin is the most potent stimulant and is the predominant catecholamine in American eel plasma (Hathaway and Epple 1989). Presumably ion and water absorption across the seawater eel intestine will be maintained by adrenalin. From the structure and the action of various agents used in the present study, structure-activity relationships of catecholamines are considered: hydroxyl groups on the benzene ring (catechol) seem to be essential for the 2-action in the seawater eel intestine and the presence of OH and CH3 on -carbon and amide, respectively, seems to potentiate the 2-action.Abbreviations ACh
acetylcholine
- AD
adrenalin
- CONH
2-cyclooctyl-2-hydroxyethylamine; n-methyltransferase
- DA
dopamine
- 5-HT
serotonin
- IBMX
3-isobutyl-1-methylxanthine
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I
sc
short-circuit current
- MCh
methacholine
- NA
noradrenalin
- PD
transepithelial potential difference
- PNMT
phenylethanolamine N-methyltransferase
-
R
t
tissue resistance |
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Keywords: | Serotonin Methacholine Catecholamine 2-receptor" target="_blank">gif" alt="agr" align="BASELINE" BORDER="0">2-receptor Adrenalin Short-circuit current Tissue resistance Eel Anguilla japonica |
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