Adenosine A2B‐receptor‐mediated cyclic AMP accumulation in primary rat astrocytes
MC Peakman, SJ Hill - British journal of pharmacology, 1994 - Wiley Online Library
MC Peakman, SJ Hill
British journal of pharmacology, 1994•Wiley Online Library1 The effects of adenosine receptor agonists and antagonists on the accumulation of cyclic
AMP have been investigated in primary cultures of rat astrocytes. 2 Adenosine A2‐receptor
stimulation caused a concentration‐dependent increase in the accumulation of [3H]‐cyclic
AMP in cells prelabelled with [3H]‐adenine. The rank order of agonist potencies was 5′‐N‐
ethylcarboxamidoadenosine (NECA; EC50= 1 μm)> adenosine (EC50= 5 μm)> 2‐
chloroadenosine (EC50= 20 μm)>> CGS 21680 (EC50> 10 μm). The presence of 0.5 μm …
AMP have been investigated in primary cultures of rat astrocytes. 2 Adenosine A2‐receptor
stimulation caused a concentration‐dependent increase in the accumulation of [3H]‐cyclic
AMP in cells prelabelled with [3H]‐adenine. The rank order of agonist potencies was 5′‐N‐
ethylcarboxamidoadenosine (NECA; EC50= 1 μm)> adenosine (EC50= 5 μm)> 2‐
chloroadenosine (EC50= 20 μm)>> CGS 21680 (EC50> 10 μm). The presence of 0.5 μm …
- 1The effects of adenosine receptor agonists and antagonists on the accumulation of cyclic AMP have been investigated in primary cultures of rat astrocytes.
- 2Adenosine A2‐receptor stimulation caused a concentration‐dependent increase in the accumulation of [3H]‐cyclic AMP in cells prelabelled with [3H]‐adenine. The rank order of agonist potencies was 5′‐N‐ethylcarboxamidoadenosine (NECA; EC50 = 1 μm) > adenosine (EC50 = 5 μm) > 2‐chloroadenosine (EC50 = 20 μm) >> CGS 21680 (EC50 > 10 μm). The presence of 0.5 μm dipyridamole, an adenosine uptake blocker, had no effect on the potency of adenosine.
- 3The response to 10 μm NECA was antagonized in a concentration‐dependent manner by the non‐selective adenosine receptor antagonists, xanthine amine congener (apparent KD = 12 nM), PD 115,199 (apparent KD = 134 nM) and 8‐phenyltheophylline (apparent KD = 126 nM). However, the A1‐receptor‐selective antagonist, 8‐cyclopentyl‐1,3‐dipropylxanthine, had no significant effect on the responses to NECA or 2‐chloroadenosine at concentrations up to 1 μm.
- 4Stimulation of A1‐receptors with the selective agonist, N6‐cyclopentyladenosine, did not alter the basal accumulation of [3H]‐cyclic AMP but inhibited a forskolin‐mediated elevation of [3H]‐cyclic AMP accumulation by a maximal value of 42%. This inhibition was fully reversed in the presence of 0.1 μm, 8‐cyclopentyl‐1,3‐dipropylxanthine.
- 5The time course for NECA‐mediated [3H]‐cyclic AMP accumulation was investigated. The results suggest that there is a substantial efflux of cyclic AMP from the cells in addition to the rapid and sustained elevation of intracellular cyclic AMP (5 fold over basal) which was also observed.
- 6These data indicate that rat astrocytes in primary culture express an A2B‐adenosine receptor coupled positively to adenylyl cyclase. Furthermore, the presence of A1‐receptors negatively coupled to adenylyl cyclase appears to have no significant effect on the A2B‐receptor‐mediated cyclic AMP responses to NECA and 2‐chloroadenosine.
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