Elalouf J M, Buhler J M, Tessiot C, Bellanger A C, Dublineau I, de Rouffignac C
Département de Biologie Cellulaire et Moléculaire, Centre d'études de Saclay, Gif-sur-Yvette, France.
J Clin Invest. 1993 Jan;91(1):264-72. doi: 10.1172/JCI116180.
Beta 1- and beta 2-adrenergic receptor (beta-ARs) expression in the thick ascending limb of rat kidney was studied at the level of mRNA and receptor coupling to adenylyl cyclase. Absolute quantitation of beta 1- and beta 2-AR mRNAs in microdissected nephron segments was performed with an assay based on reverse transcription and polymerase chain reaction, using in vitro transcribed mutant RNAs as internal standards. In the cortical thick ascending limb (CTAL), the number of mRNA molecules/mm of tubular length was 2,806 +/- 328 (n = 12) for beta 1-AR and 159 +/- 26 for beta 2-AR (P < 0.01). Lower levels were obtained in the medullary thick ascending, beta 1-AR mRNA still being predominant. The pharmacological properties of beta-ARS was also studied in the CTAL. Cyclic AMP accumulation was stimulated by beta-agonist with a rank order of potency of isoproterenol > norepinephrine > epinephrine. This observation, and the higher efficiency of a beta 1 than of a beta 2 antagonist to inhibit isoproterenol-induced cAMP accumulation, establish the typical beta 1-AR sensitivity of the CTAL. No detectable contribution of atypical or beta 3-ARs to adenylyl cyclase stimulation could be found. In conclusion, this study, which shows markedly different levels of beta 1- and beta 2-AR mRNAS in the CTAL, provides a molecular basis for the predominant expression of the beta 1 receptor subtype in this nephron segment.
在mRNA水平以及受体与腺苷酸环化酶的偶联层面，对大鼠肾脏髓袢升支粗段中β1和β2肾上腺素能受体（β-ARs）的表达进行了研究。使用基于逆转录和聚合酶链反应的检测方法，以体外转录的突变RNA作为内标，对显微切割的肾单位节段中的β1和β2-AR mRNA进行绝对定量。在皮质髓袢升支粗段（CTAL），每毫米肾小管长度的β1-AR mRNA分子数为2,806±328（n = 12），β2-AR为159±26（P < 0.01）。在髓质髓袢升支粗段中水平较低，β1-AR mRNA仍占主导。还在CTAL中研究了β-ARs的药理学特性。β-激动剂刺激环磷酸腺苷（cAMP）积累，其效力顺序为异丙肾上腺素>去甲肾上腺素>肾上腺素。这一观察结果，以及β1拮抗剂比β2拮抗剂更有效地抑制异丙肾上腺素诱导的cAMP积累，确立了CTAL典型的β1-AR敏感性。未发现非典型或β3-ARs对腺苷酸环化酶刺激有可检测到的作用。总之，这项研究表明CTAL中β1和β2-AR mRNA水平存在明显差异，为该肾单位节段中β1受体亚型的主要表达提供了分子基础。
