Moscona-Amir E, Henis Y I, Sokolovsky M
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Biochemistry. 1989 Aug 22;28(17):7130-7. doi: 10.1021/bi00443a052.
The biochemical responses to muscarinic stimulation (inhibition of isoproterenol-stimulated cAMP accumulation and stimulation of phosphoinositide turnover) were investigated in intact myocyte cultures prepared from the hearts of newborn rats. The studies employed young (5 days after plating) and aged (14 days old) myocyte cultures. Aging of the myocyte cultures was accompanied by marked alterations in both the inhibition of cAMP accumulation and the stimulation of the phosphoinositide metabolism via the muscarinic receptors. However, the effects on the two muscarinic responses were different. The first response was disrupted at the level of the coupling of the muscarinic receptors with adenylate cyclase through Gi. On the other hand, muscarinic stimulation of phosphoinositide hydrolysis still occurred in the aged myocyte cultures; however, the inositol trisphosphate generated was not converted to inositol 1-phosphate as in young cultures or as in aged cultures stimulated by norepinephrine. This raises the possibility that muscarinic activation of aged myocyte cultures shifts the metabolic state of the cells and alters the pathway of phosphoinositide hydrolysis. Treatment of aging cultures with phosphatidylcholine liposomes under conditions that yielded aged myocyte cultures with a lipid composition resembling that of young ones restored the muscarinic effect on cAMP accumulation, where the impairment in aged cultures was at the coupling stage (which takes place in the plasma membrane). This treatment had no effect on the response of the phosphoinositide metabolism to muscarinic stimulation.
在从新生大鼠心脏制备的完整心肌细胞培养物中，研究了对毒蕈碱刺激的生化反应（抑制异丙肾上腺素刺激的环磷酸腺苷（cAMP）积累和刺激磷酸肌醇代谢）。这些研究使用了年轻（接种后5天）和年老（14天大）的心肌细胞培养物。心肌细胞培养物的老化伴随着通过毒蕈碱受体对cAMP积累的抑制和对磷酸肌醇代谢的刺激这两方面的显著改变。然而，对两种毒蕈碱反应的影响是不同的。第一种反应在毒蕈碱受体通过Gi与腺苷酸环化酶偶联的水平上被破坏。另一方面，毒蕈碱对磷酸肌醇水解的刺激在年老的心肌细胞培养物中仍然发生；然而，产生的肌醇三磷酸不像在年轻培养物中或在去甲肾上腺素刺激的年老培养物中那样转化为肌醇1 - 磷酸。这增加了一种可能性，即年老心肌细胞培养物的毒蕈碱激活改变了细胞的代谢状态并改变了磷酸肌醇水解的途径。在能产生脂质组成类似于年轻细胞的年老心肌细胞培养物的条件下，用磷脂酰胆碱脂质体处理老化培养物，恢复了毒蕈碱对cAMP积累的作用，而年老培养物中的损伤发生在偶联阶段（发生在质膜）。这种处理对磷酸肌醇代谢对毒蕈碱刺激的反应没有影响。
