Regulatory mechanisms of beta-adrenergic agonists induced-cell proliferation of rat submandibular glands and their alterations during aging

细胞增殖的调节机制在衰老或癌症的生化表现中是重要的。单次注射异丙肾上腺素（IPR）到大鼠的结果在唾液腺中的DNA合成的显着刺激。本研究的目的是探讨β-受体激动剂诱导细胞增殖的机制，以及诱导细胞增殖的信号转导通路的年龄依赖性改变.从腹腔注射IPR（100 mg/kg）的大鼠下颌下腺分离细胞核。[γ-^ P] ATP孵育后，组蛋白（H）和非组蛋白（nH）从细胞核中分离出来<32>，4周时nH的磷酸化水平在注射IPR后10 h开始升高，22 h达到最高，随后恢复到对照水平。注射IPR后，启动nH磷酸化刺激或恢复到对照水平所需的时间显著增加。 ...更多信息 y与年龄。2.与choromatin相关的蛋白激酶活性的依赖性变化似乎对应于nH.3磷酸化的改变。4周龄大鼠注射IPR后14 h下颌下腺DNA中[^3H]胸腺嘧啶核苷掺入量开始增加，22 h达高峰，30 h恢复到对照水平。随着年龄的增长，大鼠下颌下腺DNA合成开始前的时间增加.在<32>IPR注射前2小时，大鼠腹腔注射[13 P]正磷酸盐，获得下颌下腺。用抗c-fos抗体免疫沉淀细胞核蛋白，SDS-PAGE电泳，放射自显影鉴定磷酸化c-fos。结论：IPR可诱导c-fos的表达，但不诱导c-jun的表达，c-fosmRNA的增龄性变化与Gs的变化密切相关。该激酶调节nH的磷酸化，nH磷酸化的延迟发生在衰老过程中的细胞增殖和细胞功能中起调节作用。少

The regulatory mechanisms of cell proliferation are important in the biochemical manifestation of senescence or cancer. A single injection of isoproterenol (IPR) into rats results in a marked stimulation of DNA synthesis in the salivary glands. The aim of this study was to investigate the mechanism of cell proliferation induced by beta-agonists and the age-dependent alteration of the signal transduction lead to the induction of cell proliferation.1. Nuclei were isolated from the submandibular glands of rats which had been injected IPR (100mg/kg) intrapeitoneally. Histone(H) and non-histone(nH) proteins were separated from nuclei after the incubation with [gamma-^<32>P] ATP.The level of phosphorylation of nH at 4-week began to increase at 10h after injection of IPR,reaching a maximum at 22h and then returned to the control level. The time after the injection of IPR required to initiate the stimulation of the phosphorylation of nH or the return to the control level increased significantl … More y with age.2. Age-dependent changes in protein kinase activity associated in the choromatin were appeared to correspond to alteration in the phosphorylation of nH.3. The incorporation of [^3H] thymidine in submandibular gland DNA of 4-week old rats was initiated at 14h after the injection of IPR,reaching a maximum at 22h and returning to the control level at 30h. The time prior to the onset of the DNA synthesis in rat submandibular glands increased during aging.4. Submandibular glands were obtained from rats which had been injected with [^<32>P] orthophosphate intraperitoneally 2h before IPR-injection. The extracted nuclear proteins were subjected to immunoprecipitation with anti-c-fos antibody, followed by SDS-PAGE.Phosphorylated c-fos was identified by autoradiography. IPR induced the expression of c-fos, but not that of c-jun. The age-dependent changes in c-fosmRNA was regarded as being closely correlated with the alteration of Gs.In conclusions, IPR stimulates protein kinase associated with the chromatin through signal transduction cascade in which receptor stimulation of adenylate cyclase increases c-fos expression. This kinase regulates the phosphorylation of nH.The delayd onset of phosphorylation of nH play a regulatory role in cell proliferation and cell function during aging. Less