Ghrelin dynamics in mice with genetically knockout of basolateral membranous receptor of the parietal cell

Ghrelin是一种由胃分泌的促进食欲的多肽，据报道，它可能通过刺激头位而增加餐前酸的输出，也可能受到副交感神经信号的影响，可能是毒碱信号。在M_1~M_5五种M受体亚型中，M_3表达于壁细胞表面，位于产生Ghrelin的A样细胞附近。本研究旨在阐明壁细胞基底外侧膜H_2受体(H_2R)或M_3受体(M_3R)基因敲除(KO)小鼠Ghrelin的动态变化。方法：研究方法。将15周龄和54周龄H_2R-KO小鼠和25周龄M_3R-KO小鼠与其窝仔进行比较。在评估了小鼠的摄食量和体重增量后，处死小鼠，用放射免疫法检测血浆活性和总ghrelin水平，用放射免疫法测定胃活性和总ghrelin水平，并测定胃液…。定量RT-PCR检测hrelin基因的表达。此外，对一些胃标本进行了Ghrelin的免疫组织化学和透射电子显微镜检查。结果。H_2R-K0小鼠的摄食量和体重增长均高于野生型小鼠。54周龄H_2R-K0小鼠的胃液pH值低于15周龄小鼠。与野生型相比，H_2R-K0小鼠胃粘膜前Proghrelin基因表达、血浆Ghrelin水平和胃粘膜Ghrelin免疫反应细胞百分率均显著增加。H_2R-KO小鼠胃内类A细胞的电子显微镜下Ghrelin阳性免疫金密度明显降低。另一方面，虽然M3RKO小鼠体重明显下降，可能反映了其营养不良，但其血浆Ghrelin水平和胃粘膜Ghrelin免疫反应细胞数与野生型小鼠相比并未显著升高。另一方面，与野生型相比，M3R-KO小鼠前促生长素基因表达和胃Ghrelin含量显著增加。结论。在H_2R-KO作为H_2R阻断的代偿机制的小鼠中，胃底类A细胞的Ghrelin的产生和分泌上调，而在M_3R-KO的小鼠中，只有Ghrelin的产生和分泌上调，而不是A类细胞的Ghrelin的产生和分泌。这些结果表明，H_2R阻断剂通过抑制胃酸分泌而影响胃促生长素的动力学，而M_3R对胃A样细胞的胃促生长素的分泌起着重要而直接的作用。较少

Ghrelin, an appetite-promoting peptide secreted from the stomach, is reported to enhance the pre-prandial acid output possibly through the stimulation of cephalic phase, and is also supposed to be affected by parasympathetic, presumably muscarinic signaling. Among five subtypes (M_1-M_5) of muscarinic acetylcholine receptors, M_3 is known to be expressed on the surface of parietal cells, which are located in the vicinity of the ghrelin-producing A-like cells. The present study was designed to clarify the dynamics of the ghrelin in mice with genetically knockout (KO) of H_2 receptor (H_2R) or M_3 receptor (M_3R) on the basolateral membrane of the parietal cell. Methods. Fifteen-and 54-week-old H_2R-KO mice and 25-week-old M_3R KO mice were compared with their littermates. After evaluating the levels of food intakes and body weight increment, mice were sacrificed to examine the plasma active and total ghrelin levels, gastric active and total ghrelin levels by RIA, and the gastric preprog … More hrelin mRNA expression by quantitative RT-PCR. Furthermore, some stomach specimens were evaluated by immunohistochemistry and transmission electron microscopy for ghrelin. Results. The levels of food intakes and body weight gain of the H_2R-K0 mice were higher than those of wild type mice. The gastric pH in the 54-week-old H_2R-K0 mice was lower than those of 15-week-old mice. Gastric preproghrelin mRNA expression, plasma ghrelin level and percentage of ghrelin-immunoreactive cells in the gastric mucosa of the H_2R-K0 mice were significantly increased as compared with those of wild types. Ghrelin-positive immunogold density in the electron micrograph was significantly reduced in A-like cells of H_2R-KO mouse stomach. On the other hand, although body weight of M_3R KO mice was significantly decreased, which possibly reflected its malnutrition, their plasma ghrelin levels and numbers of ghrelin-immunoreactive cells in the gastric mucosa were not significantly elevated as compared with those of wild type mice. On the other hand, preproghrelin mRNA expression and gastric ghrelin contents were significantly increased in M_3R-KO mice as compared with those of wild types. Conclusion. While ghrelin production and secretion from A-like cells in the gastric fundus are upregulated in mice with genetically H_2R-KO as a compensatory mechanism for H_2R blockade, only the ghrelin production, not but its secretion from A-like cells, are upregulated in mice with M_3R-KO. These results suggest that H_2R blockade affects the ghrelin dynamics through the inhibition of acid secretion and that M_3R plays an important and direct role for ghrelin secretion from A-like cells of the stomach. Less