TY - JOUR T1 - A novel irreversible antagonist of the A1-adenosine receptor. JF - Molecular Pharmacology JO - Mol Pharmacol SP - 196 LP - 205 VL - 50 IS - 1 AU - M Srinivas AU - J C Shryock AU - P J Scammells AU - J Ruble AU - S P Baker AU - L Belardinelli Y1 - 1996/07/01 UR - http://molpharm.aspetjournals.org/content/50/1/196.abstract N2 - We determined the effects of 8-cyclopentyl-3-[3-[[4-(fluorosulfonyl)benzoyl]oxy]propyl]-1-propylxanth ine (FSCPX), a putative irreversible antagonist of the A1-adenosine receptor, on cardiac A1-adenosine receptor-mediated responses and on the specific binding of [3H]-8-cyclopentyl-1,3-dipropylxanthine ([3H]CPX) to guinea pig cardiac and brain membranes. FSCPX (5 microM) completely reversed the increase in K+ current of guinea pig atrial myocytes caused by 100 microM adenosine (259 +/- 30 to 20 +/- 7 pA) but had no significant effect on K+ currents caused by either 0.5 microM carbachol or 100 microM GTP gamma S. The attenuation of K+ current by FSCPX was both time and concentration dependent and persisted after washout of the antagonist. Pretreatment of atrial myocytes with FSCPX (50 nM) markedly attenuated the activation of K+ current and the inhibition of isoproterenol-stimulated I(Ca,L) caused by adenosine by 90.1% and 84.2%, respectively, but did not alter the responses of atrial myocytes to carbachol. FSCPX (1 microM) irreversibly antagonized the A1-adenosine receptor-mediated increase in atrioventricular nodal conduction time of isolated perfused guinea pig hearts from 10.5 +/- 0.5 to 0.7 +/- 0.6 msec but did not significantly alter the A2-adenosine receptor-mediated decrease in coronary resistance. Preincubation of guinea pig cardiac membranes with 0.1, 1.0, or 3.0 microM FSCPX for 30 min reduced the Bmax of [3H]CPX binding by 41 +/- 10%, 67 +/- 6%, and 80 +/- 1% (mean +/- standard error, three experiments), respectively, with no significant change in the Kd. Similarly, 0.1 and 1.0 microM FSCPX irreversibly reduced the binding of [3H]CPX to guinea pig forebrain membranes by 65 +/- 5% and 83 +/- 2% (four experiments), respectively, but did not reduce the binding of [3H]CGS 21680, an A2a-adenosine receptor agonist, to striatal membranes. FSCPX did not affect the potency of 5'-guanylylimidodiphosphate to inhibit the binding of [3H]CCPA, an A1-adenosine receptor agonist, to brain membranes. The results indicate that FSCPX is a specific, irreversible, A1-adenosine subtype-selective receptor antagonist. ER -