DIFFERENTIAL-EFFECTS OF SURAMIN ON P-2-PURINOCEPTORS MEDIATING CONTRACTION OF THE GUINEA-PIG VAS-DEFERENS AND URINARY-BLADDER
DIFFERENTIAL-EFFECTS OF SURAMIN ON P-2-PURINOCEPTORS MEDIATING CONTRACTION OF THE GUINEA-PIG VAS-DEFERENS AND URINARY-BLADDER
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DOI：
10.1111/j.1476-5381.1994.tb13055.x
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发表时间：
1994-05-01
影响因子：
7.3
通讯作者：
HOURANI, SMO
中科院分区：
文献类型：
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作者：
BAILEY, SJ;HOURANI, SMO
1研究P-2-嘌呤受体拮抗剂苏拉明对三磷酸腺苷(ATP)和其他天然核苷三磷酸引起的豚鼠输精管和膀胱收缩的影响。2三磷酸腺苷、鸟苷(GTP)、胞苷(CTP)、肌苷(ITP)和尿苷(UTP)(0.1~500 mU M)分别收缩豚鼠输精管和豚鼠输精管。在输精管中，核苷酸的效力顺序是ATP远大于CTP和GT；GTP大于或等于UTP=ITP；在膀胱中，ATP远大于CTP=GTP，UTP=ITP，尽管这两种激动剂在两种组织中都没有达到最大反应。3苏拉明(30 mU M-1 mM)以一种明显的非竞争性方式剂量依赖地抑制ATP诱导的膀胱收缩，导致对ATP的浓度-反应曲线的斜率降低。相反，苏拉明(5 mU M~(-1)mM)对ATP引起的输精管收缩几乎没有抑制作用，100 mU M及以上浓度的苏拉明可明显增强高浓度的ATP(100~500 mM)。而CTP、GTP、UTP和ITP(1-500 mM)引起的收缩可被苏拉明(1 MM)所阻断。4用腺苷5‘-α，β-亚甲基三磷酸盐(AMPCPP)(300 MM)脱敏豚鼠输精管P-2X嘌呤受体，可在无苏拉明的情况下阻断ATP(1 mU M-1 mM)引起的收缩。然而，在苏拉明存在下诱发的收缩不受预先脱敏的影响，表明它们不是由P-2X-嘌呤受体介导的。5在本实验条件下，两种分离组织制备物都能使ATP(100 MU M)去磷酸化，2分钟后就能检测到分解产物，膀胱中的主要分解产物是肌苷，而输精管中的主要分解产物是腺苷。约35%的ATP在与膀胱孵育30min后保持完好，约45%在与输精管孵育30min后保持完好。在每个组织中，这种降解都被苏拉明(1 MM)抑制，因此在存在苏拉明的情况下，在ATP(100 MM)孵育30分钟后，大约50%留在膀胱，大约65%留在输精管中。然而，苏拉明抑制抑制激动剂腺苷的产生似乎不是在输精管中观察到的增强作用，因为P-1-嘌呤受体拮抗剂8-磺基苯茶碱(100 MM)不能减少这种增强。6二价阳离子的螯合似乎不能解释苏拉明对ATP诱导的输精管收缩的增强作用，因为当从缓冲液中去掉镁离子或当其浓度(通常为1.2 mM)增加10倍至12 mM时，或当钙离子浓度(通常为2.5 mM)降至0.83 mM时，仍可观察到增强作用。即使在没有镁离子的情况下，当钙离子浓度降至0.83 mM时，苏拉明(1 MM)也不能抑制ATP诱导的收缩。7苏拉明增强ATP诱导的输精管收缩的最可能的解释是抑制性P-2Y-嘌呤受体的共存。然而，在用KCl(35 MM)预收缩的输精管中，不能检测到对ATP(1-100mU)或对更强的P-2Y-嘌呤受体激动剂2-甲硫基三磷酸(2-MeSATP)(0.01-100mM)的持续松弛，即使在用AMPCPP(300mM)脱敏P-2X-嘌呤受体后，在KCl(35 MM)之前加入ATP(1-100mU M)或2-MeSATP(0.01-100mM)，卡巴胆碱(10MU M)或去甲肾上腺素(10MU M)不能减少随后对这些药剂的收缩。8苏拉明对ATP在膀胱和输精管引起的收缩的不同作用是意想不到的，表明ATP在这些组织中作用的受体群体可能不同。苏拉明不能抑制输精管对ATP的反应，提示输精管组织除了具有P-2X-嘌呤受体外，还可能具有苏拉明不敏感的收缩ATP受体。
1 The effect of the P-2-purinoceptor antagonist, suramin, was investigated on contractions of the guinea-pig vas deferens and urinary bladder induced by adenosine 5'-triphosphate (ATP) and by the other naturally occurring nucleoside triphosphates.2 ATP, guanosine 5'-triphosphate (GTP), cytidine 5'-triphosphate (CTP), inosine 5'-triphosphate (ITP) and uridine 5'-triphosphate (UTP) (0.1-500 mu M) each contracted both the guinea-pig bladder and the guinea-pig vas deferens. In the vas deferens the order of potency of the nucleotides was ATP much greater than CTP > GTP greater than or equal to UTP = ITP, and in the bladder it was ATP much greater than CTP = GTP, UTP = ITP, although maximal responses to these agonists were not achieved in either tissue.3 Suramin (30 mu M-1 mM) dose-dependently inhibited ATP-induced contractions of the bladder in an apparently non-competitive manner, causing a reduction in the slope of the concentration-response curve to ATP. In contrast, suramin (5 mu M-1 mM) had little inhibitory effect on ATP-induced contractions of the vas deferens, and indeed at concentrations of 100 mu M and above markedly potentiated high concentrations of ATP (100-500 mu M). The contractions induced by CTP, GTP, UTP and ITP (1-500 mu M) were, however, abolished by suramin (1 mM) in each tissue.4 Desensitization of the P-2X purinoceptors in the guinea-pig vas deferens with adenosine 5'-alpha,beta-methylenetriphosphonate (AMPCPP) (300 mu M) abolished contractions induced by ATP (1 mu M-1 mM) in the absence of suramin. However, the contractions induced in the presence of suramin were unaffected by prior desensitization, indicating that they were not mediated by P-2X-purinoceptors.5 ATP (100 mu M) was dephosphorylated by both isolated tissue preparations under the conditions of these experiments, breakdown products being detectable after 2 min, with the major breakdown product in the bladder being inosine whereas that in the vas deferens was adenosine. Approximately 35% of the ATP remained intact after incubation for 30 min with the bladder, and approximately 45% remained after incubation for 30 min with the vas deferens. In each tissue this degradation was inhibited by suramin (1 mM), so that after incubation of ATP (100 mu M) in the presence of suramin for 30 min, approximately 50% remained in the case of the bladder and approximately 65% remained in the vas deferens. However, inhibition of the production of the inhibitory agonist, adenosine by suramin did not appear to be responsible for the potentiation observed in the vas deferens, as the P-1-purinoceptor antagonist 8-sulphophenyltheophylline (100 mu M) did not reduce this potentiation.6 Chelation of divalent cations did not appear to account for the enhancement by suramin of ATP-induced contractions of the vas deferens, as the enhancement was still observed when Mg2+ was omitted from the buffer or when its concentration (normally 1.2 mM) was increased ten fold to 12 mM, or when the concentration of Ca2+ (normally 2.5 mM) was reduced to 0.83 mM. Even in the absence of Mg2+ and with the Ca2+ concentration reduced to 0.83 mM, no inhibition by suramin (1 mM) of ATP-induced contractions was observed.7 The most likely explanation for the potentiation by suramin of the ATP-induced contractions of the vas deferens is the co-existence of inhibitory P-2Y-purinoceptors. However, no consistent relaxations to ATP (1-100 mu M) Or to the more potent P-2Y-purinoceptor agonist 2-methylthioadenosine 5'-triphosphate (2-MeSATP) (0.01-100 mu M) could be detected in the vas deferens precontracted with KCl (35 mM), even after desensitization of P-2X-purinoceptors with AMPCPP (300 mu M) Similarly, ATP (1-100 mu M) or 2-MeSATP (0.01-100 mu M) added before KCl (35 mM), carbachol (10 mu M) or noradrenaline (10 mu M) did not reduce subsequent contractions to these agents.8 The differential effect of suramin on the contractions induced by ATP in the bladder and the vas deferens was unexpected, and shows that the receptor populations by which ATP acts in these tissues may not be identical. The failure of suramin to inhibit responses to ATP in the vas deferens suggests that this tissue, in addition to possessing P-2X-purinoceptors may also possess a suramin-insensitive contractile ATP receptor revealed in the presence of suramin.