Affinities of catecholamines for extraneuronal uptake in smooth muscle cells in trachealis muscle of guinea-pig

Bryan L.J. and O'Donnell S.R. (1980) Affinities of catecholamines for extraneuronal uptake in smooth muscle cells in trachealis muscle of guinea-pig. Naunyn-Schmiedeberg's Archives of Pharmacology, 311 2: 139-146. doi:10.1007/BF00510252


Author Bryan L.J.
O'Donnell S.R.
Title Affinities of catecholamines for extraneuronal uptake in smooth muscle cells in trachealis muscle of guinea-pig
Journal name Naunyn-Schmiedeberg's Archives of Pharmacology   Check publisher's open access policy
ISSN 0028-1298
Publication date 1980
Sub-type Article (original research)
DOI 10.1007/BF00510252
Volume 311
Issue 2
Start page 139
End page 146
Total pages 8
Publisher Springer-Verlag
Subject 3004 Pharmacology
Abstract 1. Tracheal segments from guinea-pigs pretreated with 6-hydroxydopamine were incubated with adrenaline, noradrenaline or isoprenaline at 37° C for various time intervals. Catechol-O-methyl transferase was inhibited by 100 μM U-0521. Tissues were prepared for fluorescence histochemistry and accumulated catecholamine in trachealis smooth muscle cells measured by fluorescence microphotometry. 2. The monoamine oxidase inhibitor, pargyline, markedly enhanced the accumulation of noradrenaline, but did not affect accumulation of isoprenaline. Pargyline (100 μM) was included in all further experiments with adrenaline or noradrenaline, but not in those with isoprenaline. 3. Net uptake into the smooth muscle cells approached steady state after incubation with amine for 60-120 min. The uptake of amine was linearly related to time for up to 10 min with 5 μM adrenaline, noradrenaline and isoprenaline and with 800 μM noradrenaline, but was linear only up to 5 min for 800 μM adrenaline and isoprenaline. Thus, an incubation time with amine of 5 min was selected for the initial rate kinetic study. 4. The uptake of the three catecholamines into the smooth muscle cells obeyed Michaelis-Menten saturation kinetics. The mean Km values for adrenaline, noradrenaline and isoprenaline were 151 μM, 238 μM and 273 μM respectively. Hence, the affinities of the three catecholamines for extraneuronal uptake in the trachealis smooth muscle cells are of the same order of magnitude. Adrenaline may have a slightly higher affinity than the other two amines. This is contrary to the accepted generalization that isoprenaline has a higher affinity for extraneuronal uptake than adrenaline or noradrenaline.
Keyword Catecholamines
Extraneuronal uptake
Fluorescence microphotometry
Guinea-pig trachealis smooth muscle
Kinetics
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: Scopus Import
 
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