IMPAIRED GALLBLADDER CONTRACTION WITH GALLSTONES

肌肉收缩缺陷导致的胆汁淤积被认为起了作用。 在胆结石的形成和生长中起着允许的作用，可能是一个主要的 胆结石复发的促成因素。这是有缺陷的 人类和草原犬的胆囊壁收缩与 过多的胆汁胆固醇，其特征是对 受体依赖的配体，如CCK-8和乙酰胆碱。CCK-8不支持 充分激活受损肌肉细胞的可用细胞内通路 在功能上看起来很正常。控制肌的收缩 低浓度CCK-8诱导的细胞是由PKC介导的，而 高浓度诱导的钙调素依赖于钙调素。相比之下， CCK-8对缺陷性肌细胞的收缩作用 浓度只能利用PKC途径。规模的大小 这些有缺陷的肌肉细胞的收缩在膜 用GTP-Gamma直接激活G蛋白绕过受体 或通过利用第二信使，如IP3和DAG，或通过钙调蛋白。 这些数据表明，缺陷可能存在于信号转导。 穿过质膜可能是由于过量掺入 胆固醇，可影响其脂质环境和跨膜蛋白。 这一假设得到了我们的初步发现的支持：1)正常 与富含胆固醇的脂质体孵育的肌肉细胞增加了 质膜中胆固醇与磷脂(CH：P1)的比值及其发育 对CCK反应的有缺陷的收缩，在治疗后恢复正常 有GTP伽玛病；2)异常的CH：P1比率和缺陷 胆固醇结石引起的胆囊肌细胞收缩 与无胆固醇脂质体孵育后恢复正常。 因此，我们建议研究对照和缺陷肌肉细胞 来自人类和土拨鼠的胆囊壁：1)胆固醇的直接作用 在肌肉收缩和松弛缺陷的发病机制中；2) 调节收缩和松弛的第二信使的产生 由受体依赖的配体和激动剂诱导 3)对照和对照细胞质膜的变化。 富含胆固醇的培养前后有缺陷的肌肉细胞 和无胆固醇脂质体通过测量其胆固醇：磷脂 4)膜功能异常。 通过测量配基结合来检测这些缺陷肌肉细胞中的受体， 受体-G蛋白偶联和G蛋白的受体激活； 这些与胆固醇相关的肌肉异常是否可逆 体外与无胆固醇脂质体孵育和体内孵育后 无胆固醇或低胆固醇饮食。

Gallbladder stasis due to a defective muscle contraction is thought to play a permissive role in gallstone formation and growth and may be a major contributing factor in the recurrence of gallstones. This defective gallbladder contraction in humans and prairie dogs is associated with excess bile cholesterol and is characterized by a reduced response to receptor-dependent ligands such as CCK-8 and acetylcholine. CCK-8 does not fully activate available intracellular pathways of defective muscle cells that appear to be functionally normal. The contraction of control muscle cells induced by low concentrations of CCK-8 is mediated by PKC, whereas that induced by high concentrations is calmodulin dependent. In contrast, the contraction of defective muscle cells induced by all CCK-8 concentrations can only utilize the PKC pathway. The magnitude of contraction of these defective muscle cells is normalized when membrane receptors are circumvented by directly activating G proteins with GTPgammas or by utilizing second messengers such as IP3 and DAG or by calmodulin. These data suggest that the defect may lie in the signal transduction across the plasma membrane possibly due to excessive incorporation of cholesterol which could affect its lipid milieu and transmembrane proteins. This hypothesis is supported by our preliminary findings: 1) that normal muscle cells incubated with cholesterol-rich liposomes increased their cholesterol:phospholipid (Ch:P1) ratio in the plasma membrane and develop a defective contraction in response to CCK which is normalized when treated with GTPgammas; and, 2) that the abnormal Ch:P1 ratio and defective contraction of muscle cells from gallbladders with cholesterol stones are normalized after incubation with cholesterol-free liposomes. We therefore propose to investigate in control and defective muscle cells from human and prairie dog gallbladders: 1) the direct role of cholesterol in the pathogenesis of the defective muscle contraction and relaxation; 2) the generation of second messengers that mediate contraction and relaxation induced by receptor-dependent ligands and by agonists that circumvent membrane receptors; 3) the changes of the plasma membrane of control and defective muscle cells before and after incubation with cholesterol-rich and cholesterol-free liposomes by measuring its cholesterol:phospholipid ratio and membrane fluidity; 4) the functional abnormalities of membrane receptors in these defective muscle cells by measuring ligand binding, receptor-G protein coupling and receptor activation of G proteins; and, 5) whether these cholesterol associated muscle abnormalities are reversible in vitro after incubation with cholesterol-free liposomes and in vivo after cholesterol-free or low cholesterol diets.