Dixon C J, Woods N M, Webb T E, Green A K
Department of Human Anatomy and Cell Biology, The University of Liverpool, Ashton Street, Liverpool, L69 3GE.
Br J Pharmacol. 2000 Feb;129(4):764-70. doi: 10.1038/sj.bjp.0703103.
Previous studies have indicated the expression of multiple P2Y receptors by rat hepatocytes although they have not been identified. Here we show by reverse transcriptase-polymerase chain reaction (RT - PCR) that rat hepatocytes express mRNA encoding all of the four cloned rat P2Y receptors (P2Y(1), P2Y(2), P2Y(4) and P2Y(6)). The effects of UTP have been examined on single aequorin-injected rat hepatocytes. The Ca(2+) transients induced by UTP were indistinguishable from those induced by ATP in the same cell. The modulatory effects of elevated intracellular cyclic AMP concentration were the same on both UTP- and ATP-induced Ca(2+) transients. UDP, an agonist at the P2Y(6) receptor, failed to induce transients in hepatocytes, indicating that functional P2Y(6) receptors coupled to increased Ca(2+) are not expressed. The transients evoked by ADP were more sensitive to inhibition by suramin than those induced by either ATP or UTP. Within an individual cell, the transients induced by ATP and UTP were inhibited by the same concentration of suramin. This sensitivity of ATP and UTP responses to suramin suggests action through P2Y(2) rather than P2Y(4) receptors. Co-application of 30 microM pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) caused a decrease in frequency and amplitude of transients induced by ADP. ATP- and UTP-induced transients also displayed a decrease in amplitude in response to addition of PPADS, but this was accompanied by an increase in frequency of transients. In conclusion the data presented here are consistent with the co-expression of P2Y(1) and P2Y(2) receptors by rat hepatocytes.
以往研究表明，大鼠肝细胞可表达多种P2Y受体，尽管尚未鉴定出来。在此，我们通过逆转录聚合酶链反应（RT-PCR）表明，大鼠肝细胞表达编码所有四种克隆的大鼠P2Y受体（P2Y(1)、P2Y(2)、P2Y(4)和P2Y(6)）的mRNA。我们研究了UTP对单个注射水母发光蛋白的大鼠肝细胞的影响。UTP诱导的[Ca(2+)]i瞬变与同一细胞中ATP诱导的瞬变无法区分。细胞内环磷酸腺苷浓度升高对UTP和ATP诱导的[Ca(2+)]i瞬变的调节作用相同。UDP是P2Y(6)受体的激动剂，但未能在肝细胞中诱导瞬变，这表明未表达与[Ca(2+)]i增加偶联的功能性P2Y(6)受体。ADP诱发的瞬变更易受苏拉明抑制，而不是ATP或UTP诱导的瞬变。在单个细胞内，ATP和UTP诱导的瞬变受相同浓度苏拉明的抑制。ATP和UTP反应对苏拉明的这种敏感性表明其作用是通过P2Y(2)而非P2Y(4)受体。共同应用30 microM磷酸吡哆醛-6-偶氮苯基-2',4'-二磺酸（PPADS）会导致ADP诱导的瞬变频率和幅度降低。ATP和UTP诱导的瞬变在加入PPADS后也显示幅度降低，但同时瞬变频率增加。总之，此处给出的数据与大鼠肝细胞共表达P2Y(1)和P2Y(2)受体一致。
