4-acetamido-4--isothiocyanatostilbene-2-2--disulfonic-acid and alpha-beta-methyleneadenosine-5--triphosphate

ATP and UTP contracted guinea pig isolated, perfused trachea and were more potent when applied to the mucosal (intraluminal, IL) surface than when applied to the serosal (extraluminal, EL) surface. IL ATP and IL UTP were equipotent (ATP approximately UTP); EL ATP was 7-fold more potent than EL UTP (ATP > UTP). beta, gamma-Methylene ATP was nearly devoid of activity. Epithelium (Epi) removal decreased IL ATP potency and EL and IL maximum response magnitude, but elevated the IL UTP maximum response. In the presence of EL and IL indomethacin (3 x 10(-6) M; +/- Epi) to inhibit cyclo-oxygenase, or beta, gamma-methylene ATP (10(-4) M) to desensitize receptors, contractions to ATP were abolished, but those to UTP were not. Cl- channel blockade with 4,4'-diisothiocyano-2,2'-stilbene disulfonate (DIDS; 10(-4) M; +/- Epi) and sodium channel blockade with amiloride (10(-4) M; +/- Epi) antagonized contractions to EL and IL ATP and UTP. DIDS and amiloride did not inhibit contractions to methacholine; IL reactivity to methacholine was potentiated by indomethacin and Epi removal. Our findings indicate that the Epi facilitates contraction to ATP, which involves an atypical P2 purinoceptor, prostanoids, and Na+ and Cl- channels. Contractile responses to UTP involve a different receptor, and are neither facilitated by the Epi nor mediated by prostanoids, but involve these channels.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Adenosine Triphosphate; Amiloride; Animals; Chloride Channels; Epithelium; Guinea Pigs; In Vitro Techniques; Indomethacin; Kinetics; Male; Membrane Proteins; Methacholine Chloride; Muscle Contraction; Muscle, Smooth; Nucleotides; Perfusion; Prostaglandins; Receptors, Purinergic; Sodium Channels; Trachea; Uridine Triphosphate

In higher concentrations (> 3 x 10(-4) M) than those causing contractile responses. ATP relaxed the smooth muscle of the guinea pig perfused trachea. Here we examined the relaxant effects of nucleotides. ATP and its nonhydrolyzable congener, beta, gamma-methylene ATP (APPCP), were approximately 4- and approximately 117-fold, respectively, more potent when applied separately to the serosal (extraluminal, EL) surface compared to the mucosal (intraluminal, IL) surface of methacholine (3 x 10(-7) M; EL)-contracted tracheae. APPCP was orders of magnitude more potent than ATP in both EL and IL compartments. EL UTP did not cause relaxation; IL UTP was nearly devoid of activity. The order of EL and IL activity (APPCP >> ATP) was unusual for nucleotide-induced relaxation of smooth muscle. Relaxation to ATP was not inhibited by the Cl- channel blocker 4,4'-diisothiocyano-2,2'-stilbene disulfonate (10(-4) M) or by the cyclo-oxygenase inhibitor indomethacin (3 x 10(-6) M), in contrast to the inhibitory effects of these drugs on contraction to ATP. The adenosine receptor antagonist 8-phenyltheophylline (10(-6) M) had no effect on relaxation to ATP or APPCP. Our findings indicate that Cl- channels, prostaglandins and adenosine are not involved in relaxation to adenine nucleotides.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Adenosine; Adenosine Triphosphate; Animals; Chloride Channels; Guinea Pigs; In Vitro Techniques; Indomethacin; Male; Membrane Proteins; Mucous Membrane; Muscle Relaxation; Muscle, Smooth; Nucleotides; Prostaglandins; Theophylline; Trachea; Uridine Triphosphate