INHIBITION OF ATP-INDUCED CAMP FORMATION BY 5'-P-FLUOROSULFONYLBENZOYLADENOSINE IN NG108-15 CELLS

ATP is known to increase intracellular cAMP levels in NG108-15 cells v ia a novel purinoceptor and this response is inhibited by the P-1, pur inoceptor antagonist methylxanthine. In the present study, we examined the ef effects of 5'-p-fluorosulfonylbenzoyladenosine (FSBA), an affi nity ligand for ATP-binding proteins, on cAMP formation mediated by ac tivation of adenylate cyclase (AC)linked purinoceptors in NG108-15 cel ls. cAMP levels were determined by RIA using an anti-succinyl-cAMP ant iserum. FSBA (100 mu M) increased intracellular cAMP about 2.6-fold Ho wever, FSBA-induced cAMP formation was abolished by pretreatment with adenosine deaminase, suggesting that adenosine, a breakdown product of FSBA, is involved in FSBA-induced cAMP formation. In contrast, pretre atment of cells with FSBA in the presence of adenosine deaminase inhib ited cAMP formation induced by ATP and beta,gamma-methylene-ATP (beta, gamma-MeATP), without affecting the prostaglandin E-1 (PGE(1))-induced response. The inhibitory effect of FSBA on ATP-induced cAMP formation was concentration-dependent with a concentration required for half-ma ximal inhibition (IC50) of around 3 mu M The inhibitory effect of FSBA was not affected by pertussis toxin (PTX)-treatment. Pretreatment wit h FSBA (10 mu M) depressed the maximal response to beta,gamma-MeATP by 60%, but did not affect the response to 5'-N-ethylcarboxamidoadenosin e. The inhibitory effect of FSBA (100 mu M) increased time-dependently during pretreatment and partly resisted wash-out. The inhibition by F SBA was protected by simultaneous addition of beta,gamma-MeATP during the FSBA pretreat ment, indicating that both FSBA and the ATP analogue interacted with the same receptor site. The pretreatment with FSBA di d not affect the increase in [Ca2+](i) induced by ATP, UTP or benzoylb enzoic ATP. These results suggest that FSBA inhibits cAMP accumulation induced in NG108-15 cells by ATP or related agonists by selective mod ification of an AC-linked purinoceptor.