Giaroni Cristina, Knight Gillian E, Zanetti Elena, Chiaravalli Anna Maria, Lecchini Sergio, Frigo Gianmario, Burnstock Geoffrey
Clinical and Applied Pharmacology Centre, University of Insubria, I-21100 Varese, Italy.
Neuropharmacology. 2006 May;50(6):690-704. doi: 10.1016/j.neuropharm.2005.11.015. Epub 2006 Jan 23.
The actions of purine and pyrimidine compounds on isolated segments of the mouse intestine were investigated during postnatal development. The localization of P2Y(1), P2Y(2), P2Y(4), P2X(1,) P2X(2) and P2X(3) receptors were examined immunohistochemically, and levels of expression of P2Y(1), P2X(1) and P2X(2) were studied by Western immunoblot. From day 12 onwards, the order of potency for relaxation of longitudinal muscle of all regions was 2-MeSADP>or=alpha,beta-meATP>or=ATP=UTP=adenosine, suggesting P2Y(1) receptors. This was supported by the sensitivity of responses to 2-MeSADP to the selective antagonist MRS 2179 and P2Y(1) receptor immunoreactivity on longitudinal muscle and a subpopulation of myenteric neurons. A further alpha,beta-meATP-sensitive P2Y receptor subtype was also indicated. ATP and UTP were equipotent suggesting a P2Y(2) and/or P2Y(4) receptor. Adenosine relaxed the longitudinal muscle in all regions via P1 receptors. The efficacy of all agonists to induce relaxation of raised tone preparations increased with age, being comparable to adult by day 20, the weaning age. During postnatal development the contractile response of the ileum and colon was via P2Y(1) receptors, while the relaxant response mediated by P2Y(1) receptors gradually appeared along the mouse gastrointestinal tract, being detectable in the stomach from day 3 and in the duodenum from day 6. In the ileum and colon relaxant responses to 2-MeSADP were not detected until days 8 and 12, respectively. 2-MeSADP induced contractions on basal tone preparations from day 3, but decreased significantly at day 12 and disappeared by day 20. At day 8, contractions of colonic longitudinal muscle to ATP showed no desensitisation suggesting the involvement of P2X(2) receptors. Immunoreactivity to P2X(2) receptors only was observed on the longitudinal muscle of the colon and ileum from day 1 and on a subpopulation of myenteric neurons from day 3. These data suggest that P2Y(1) receptors undergo postnatal developmental changes in the mouse gut, with a shift from contraction to relaxation. Such changes occur 1 week before weaning and may contribute to the changes that take place in the gut when the food composition changes from maternal milk to solid food.
在出生后发育过程中，研究了嘌呤和嘧啶化合物对小鼠离体肠段的作用。采用免疫组织化学方法检测了P2Y(1)、P2Y(2)、P2Y(4)、P2X(1)、P2X(2)和P2X(3)受体的定位，并通过蛋白质免疫印迹法研究了P2Y(1)、P2X(1)和P2X(2)的表达水平。从出生后第12天起，所有区域纵肌舒张的效力顺序为2-甲硫腺苷二磷酸≥α,β-甲硫腺苷三磷酸≥三磷酸腺苷=三磷酸尿苷=腺苷，提示为P2Y(1)受体。这一结果得到了对2-甲硫腺苷二磷酸反应对选择性拮抗剂MRS 2179的敏感性以及纵肌和一部分肌间神经元上P2Y(1)受体免疫反应性的支持。还表明存在另一种对α,β-甲硫腺苷三磷酸敏感的P2Y受体亚型。三磷酸腺苷和三磷酸尿苷效力相当，提示为P2Y(2)和/或P2Y(4)受体。腺苷通过P1受体使所有区域的纵肌舒张。所有激动剂诱导升高张力制剂舒张的效力随年龄增加，在出生后第20天（断奶年龄）与成年鼠相当。在出生后发育过程中，回肠和结肠的收缩反应通过P2Y(1)受体介导，而由P2Y(1)受体介导的舒张反应在小鼠胃肠道中逐渐出现，在出生后第3天可在胃中检测到，第6天可在十二指肠中检测到。在回肠和结肠中，对2-甲硫腺苷二磷酸的舒张反应分别直到出生后第8天和第12天才检测到。2-甲硫腺苷二磷酸从出生后第3天起在基础张力制剂上诱导收缩，但在第12天显著降低，到第20天消失。在出生后第8天，结肠纵肌对三磷酸腺苷的收缩未出现脱敏现象，提示涉及P2X(2)受体。仅在出生后第1天在结肠和回肠的纵肌上以及第3天在一部分肌间神经元上观察到对P2X(2)受体的免疫反应性。这些数据表明，P2Y(1)受体在小鼠肠道中经历出生后发育变化，从收缩转变为舒张。这种变化在断奶前1周发生，可能有助于解释当食物组成从母乳转变为固体食物时肠道中发生的变化。
