A 1 and A 2 adenosine receptors regulate adenylate cyclase in cultured human lung fibroblasts

Abstract

Adenosine stimulates and inhibits adenylate cyclase activity and cAMP levels in WI-38 and VA13 fibroblasts. The inhibitory effects appear to be mediated by both A 1 receptors and the P-site. Results supporting these conclusions are as follows: (1) Adenosine by itself increased cAMP accumulation in these cells. (2) PGE 1-stimulated cAMP accumulation was inhibited by adenosine in a concentration-dependent fashion. (3) IAP treatment blocked adenosine inhibition of cAMP accumulation and adenylate cyclase activity and enhanced adenosine stimulation of cAMP accumulation in VA13 cells. (4) Theophylline and MIX attenuated adenosine inhibition of cAMP accumulation. (5) Adenosine analogs with substitutions in the purine ring inhibited PGE 1-stimulated cAMP accumulation and adenylate cyclase activity. (6) PGE 1-stimulated cAMP accumulation was inhibited by the P-site agonist 2′5′-dideoxyadenosine, but this inhibition was not attenuated by MIX or IAP treatment. These data support the idea that adenosine may inhibit cAMP accumulation in VA13 or WI-38 cells by acting at an A 1 receptor of the P-site. The decrease in cAMP accumulation mediated by the A 1 receptor appeared to be due at least in part to an N i-mediated inhibition of adenylate cyclase.