High‐ and low‐affinity binding sites for [³H]‐α,β‐methylene ATP in rat urinary bladder membranes

Comparative studies on the affinities of ATP derivatives for P2X‐purinoceptors in rat urinary bladder

“…Divalent cations can facilitate the degradation of ATP and its derivatives and influence the interaction of purine compounds with P2X-purinoceptors (Bo & Burnstock, 1990 Burnstock & Kennedy (1985). It should also be mentioned that the Hill coefficients for the displacement curves of ATP and ADP have been reduced greatly (from 1.53 to 0.85 for ATP, and from 1.45 to 0.90 for ADP).…”

“…First the compounds which are commonly used to distinguish PI-, P2-, P2X-, and P2Y-purinoceptors were examined again, since the experimental conditions in this study were different from those reported in a previous paper (Bo & Burnstock, 1990). Divalent cations can facilitate the degradation of ATP and its derivatives and influence the interaction of purine compounds with P2X-purinoceptors (Bo & Burnstock, 1990 Burnstock & Kennedy (1985).…”

Autoradiography of P2X ATP receptors in the rat brain

“…Furthermore, although Michel & Humphrey (1993) Bo & Burnstock, 1990) to membranes prepared from rat cerebral cortex, only a brief report (Bo & Burnstock, 1994) (Young & Kuhar, 1979) with some modifications (Greenamyre et al, 1985;Li & Balcar, 1994;Balcar et al, 1995). Sections were preincubated at room temperature (22-25°C) for 30 min with two changes of medium (50 mM Tris-HCl, pH 7.4, used throughout), then incubated in the presence of 3H-labelled [3H]-,P-MeATP at 2-4°C for 40 min, washed, dried and either extracted with 0.25 M NaOH for liquid scintillation counting (LCS) and protein determination (Lowry et al, 1951) (Li & Balcar, 1994;Balcar et al, 1995 (Levitzki, 1980).…”

P2Y receptor-mediated transient relaxation of rat longitudinal ileum preparations involves phospholipase C activation, intracellular Ca2+ release and SK channel activation

“…This blocker was added to the organ bath 10 min prior to ATP application and almost abolished both relaxation (100 µmol/L α,β-Me-ATP: -1.2±0.6 mN, n=6, P<0.01, unpaired t-test) and contraction (100 µmol/L α,β-Me-ATP: 2.8±0.7 mN, n=6, P<0.05, unpaired t-test), hence providing evidence that P2 receptoractivation is the predominant mechanism of action of α,β-Me-ATP ( Figure 1B, C). While α,β-Me-ATP has been reported to act primarily on P2X receptors [24] , we aimed to determine whether the P2 receptor-induced transient relaxation could also be achieved by 2-Me-S-ADP, a non-hydrolyzable agonist with preferential action on P2Y receptors. At a concentration of 10 µmol/L, this compound also produced transient relaxation (-6.7±0.9 mN, n=20) but less pronounced contraction (3.7±1.3 mN, n=20).…”

“…These data suggest that the α,β-Me-ATP-induced relaxation is preferentially mediated by the P2Y 1 and P2Y 13 receptors but may also involve other receptors, while the 2-Me-S-ADP-induced relaxation is mediated by P2Y 6 receptor activation ( Figure 6B). P2 receptors are involved in purinergic motility of the rat ileum The purinergic agonist α,β-Me-ATP was introduced as an inhibitor of ionotropic P2X receptors [24,29] . However, Kitajima and co-workers have demonstrated that the α,β-Me-ATPinduced rise in the intracellular Ca 2+ in aortic smooth muscle cells is not entirely prevented by verapamil, which indicates the involvement of non-L-type voltage-dependent Ca 2+ channels and/or intracellular Ca 2+ release following P2Y receptor activation [30] .…”