EFFECT OF 5'-(N-ETHYLCARBOXAMIDO)ADENOSINE ON ADENOSINE TRANSPORT IN CULTURED CHROMAFFIN CELLS

被引:31
作者
DELICADO, EG
RODRIGUES, A
SEN, RP
SEBASTIAO, AM
RIBEIRO, JA
MIRASPORTUGAL, MT
机构
[1] UNIV COMPLUTENSE MADRID,FAC VET,DEPT BIOQUIM,E-28040 MADRID,SPAIN
[2] GULBENKIAN INST SCI,PHARMACOL LAB,OEIRAS,PORTUGAL
关键词
5′‐(N‐Ethylcarboxamido)adenosine; Adenosine receptors; Adenosine transport; Chromaffin cells; Nitrobenzylthioinosine; Nucleoside transport;
D O I
10.1111/j.1471-4159.1990.tb04895.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Abstract: Extracellular adenosine is transported into chromaffin cells by a high‐affinity transport system. The action of adenosine receptor ligands was studied in this cellular model 5‐(N‐Ethylcarboxamido)adenosine (NECA), an agonist receptors, activated adenosine transport. Km values for adenosine were 4.6 ± 1.0 (n = 5) and 10.2 ± 3.0 μM (n = 5) for controls and 100 nM NECA, respectively. The Vmax values were 66.7 ± 23.5 and 170.2 ± 30 pmol/106 cells/min for control and 100 nM NECA, respectively. The A1 agonist N6‐cyclohexyladenosine, the A1 antagonist 8‐cyclopentyl‐1, 3‐dipropylxanthine, and the A1‐A2 antagonist 1,3‐dipropyl‐8‐{4‐[(2‐aminoethyl)amino]‐carbonylmethyloxyphenyl}‐xanthine did not significantly modify the adenosine transport in this system. Binding studies done with [3H]dipyridamole, a nucleoside transporter ligand, did not show changes in either the number or affinity of transporter sites after NECA treatment. This ligand can enter cells and quantifies the total number of transporters. The binding studies with [3H]‐nitrobenzylthioinosine, which quantifies the plasma membrane transporters, showed a Bmax of 19,200 ± 800 and 23,200 ± 700 transporters/cell for controls and 100 nM NECA, repectively. No changes in the KD were obtained. The effects of NECA were not mediated through adenylate cyclase activation, because its action was not imitated by forskolin. Copyright © 1990, Wiley Blackwell. All rights reserved
引用
收藏
页码:1941 / 1946
页数:6
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