Identification of histamine H_1 receptor subtypes

采用蔗糖密度梯度离心分离法分离牛肾上腺髓质mRNA，分别注射到非洲爪蟾卵母细胞中。电生理检测组胺H_1受体的表达。注射含有3.5 kb mRNA或5.0 kb mRNA的组分可诱导组胺H_1受体的表达。这表明存在组胺H_1受体亚型。组胺H_1受体依赖的内向Cl^-电流约为。注射3.5 kb mRNA时为50nA，注射5.0 kb mRNA时小于40nA。利用体外转录载体lambda ZAPII构建3.5 kb mRNA和5.0 kb mRNA的cDNA文库。通过体外转录和电生理检测组胺H_1受体表达，注射mRNA筛选cDNA文库。从3.5 kb mRNA中分离得到组胺H_1受体cDNA，并测定其结构。注射体外转录mRNA后，5.0 kb mRNA片段无法检测组胺H_1受体依赖的内向Cl^-电流。最近制备了组胺H_1受体敲除小鼠，并通过[^3H] mepyramine结合的放射自显影证实了组胺H_1受体缺失。这表明小鼠只有一个组胺H_1受体基因。我们观察到人和豚鼠具有两种不同分子量的组胺H_1受体mrna。组胺的生理和病理作用因物种而异，在人和豚鼠中仍然存在组胺H_1受体亚型的可能性。

mRNA derived from bovine adrenal medulla was fractionated by the sucrose density gradient centrifugation, and each fraction was injected into Xenopus Laevis oocytes. Expression of histamine H_1 receptors was electrophysiologically examined. Injection of fractions containing 3.5-kb mRNA or 5.0-kb mRNA induced the expression of histamine H_1 receptors. This result suggests the existence of histamine H_1 receptor subtypes. Histamine H_1 receptor-dependent inward Cl^- current was aprox. 50nA when 3.5-kb mRNA was injected, and smaller than 40nA when 5.0-kb mRNA was injected. cDNA libraries derived from 3.5-kb mRMA and 5.0-kb mRNA were constructed using lambda ZAPII,a vector for in vitro transcription. The cDNA library was screened by the injection of mRNA through in vitro transcription and electrophysiological detection of histamine H_1 receptor expression. The histamine H_1 receptor cDNA derived from 3.5-kb mRNA was isolated, and the structure of the receptor was determined. The detection of histamine H_1 receptor-dependent inward Cl^- current from 5.0-kb mRNA fraction was not succeeded when mRNA through in vitro transcription was injected. Recently histamine H_1 receptor knock out mouse was prepared, and the lack of histamine H_1 receptors was demonstrated by the autoradiography of [^3H] mepyramine binding. This result indicated that mouse has only one histamine H_1 receptor gene. We observed that human and guinea pig have two kinds of histamine H_1 rceptor mRNAs with different molecular weights. Physiological and pathological roles of histamine differ from species, and the possibility of histamine H_1 receptor subtypes in human and guinea pig still remains.