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Adenosine A 1 ‐receptor stimulated increases in intracellular calcium in the smooth muscle cell line, DDT 1 MF‐2
Author(s) -
Dickenson John M.,
Hill Stephen J.
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb13444.x
Subject(s) - adenosine , extracellular , calcium , adenosine receptor antagonist , medicine , endocrinology , chemistry , agonist , ryanodine receptor , adenosine receptor , pertussis toxin , receptor , biology , biochemistry , g protein
1 The effect of a range of adenosine receptor agonists on intracellular free calcium concentration ([Ca 2+ ] i ) has been studied in the hamster vas deferens smooth muscle cell line DDT 1 MF‐2. 2 Adenosine receptor agonists elicited a rapid and maintained increase in [Ca 2+ ] i in fura‐2 loaded DDT 1 MF‐2 cells. The initial rise could be maintained in the absence of extracellular calcium, whereas the maintained or plateau phase was dependent upon the presence of extracellular calcium and appeared to be associated with calcium influx. The rank order of agonist potencies was N 6 ‐cyclopentyladenosine > 5′‐N‐ethylcarboxamidoadenosine > 2‐chloroadenosine > adenosine. 3 The response to 2‐chloroadenosine was antagonized by the antagonists 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX, K D 0.14 n m ) and 8‐phenyltheophylline ( K D 112 n m ). 4 Pretreatment with the 5‐lipoxygenase inhibitor AA861 (20 μ m ) produced only a small (14 ± 2%) inhibition of the [Ca 2+ ] i response elicted by N 6 ‐cyclopentyladenosine (300 n m ), in nominally Ca 2+ ‐free buffer containing 0.1 m m EGTA. The cyclo‐oxygenase inhibitor, indomethacin (2 μ m ) was without effect. 5 The Ca 2+ ‐influx associated with the plateau phase required the continued presence of agonist on the receptor. The antagonist DPCPX (100 n m ) attenuated the rise in [Ca 2+ ] i observed when extracellular Ca 2+ was re‐applied after the cells had been stimulated with N 6 ‐cyclopentyladenosine (CPA;300 n m ) in experiments initiated in nominally Ca 2+ ‐free buffer. 6 Pretreatment with pertussis toxin (200 ng ml −1 for 4 h) inhibited the CPA (100 n m ) stimulated intracellular Ca 2+ release and Ca 2+ influx but was without effect on the response to histamine (100 μ m ). 7 These data suggest that adenosine A 1 ‐receptor activation in DDT 1 MF‐2 cells stimulates release of Ca 2+ from intracellular stores and influx of extracellular Ca 2+ through Ca 2+ entry pathways in the plasma membrane which required the continued presence of agonist on the receptor.