Yasuda G, Sun L, Lee H C, Umemura S, Jeffries W B
Second Department of Internal Medicine, Yokohama City University School of Medicine, Japan.
Am J Physiol. 1996 Sep;271(3 Pt 2):F762-9. doi: 10.1152/ajprenal.1996.271.3.F762.
We investigated beta-adrenoceptor subtype(s) expressed in cultured rat inner medullary collecting duct (IMCD) cells. In radioligand binding assay, [125I]iodocyanopindolol bound to IMCD cell membranes, representing a single class of binding sites (dissociation constant = 96.1 pM, maximum binding capacity = 18.2 fmol/mg protein, n = 8). In competition studies, ICI-89406 (beta 1-antagonist) and ICI-118551 (beta 2-antagonist) bound with high affinity, fitting a two-site model. Isoproterenol increased intracellular adenosine 3',5'-cyclic monophosphate (cAMP) accumulation (half-maximal effective concentration = 200 nM). Propranolol completely inhibited isoproterenol-induced cAMP accumulation [half-maximal inhibitory concentration (IC50) = 270 nM]. ICI-89406 and ICI-118551 inhibited cAMP accumulation by 50% (IC50 = 1.5 microM and 1.7 microM, respectively). The combined addition of ICI-89406 and ICI-118551 resulted in a curve indistinguishable from that of propranolol. The beta 1- and beta 2-adrenoceptor mRNAs have been demonstrated using reverse transcription-polymerase chain reaction. In initial and terminal IMCD cells, propranolol (3 microM) inhibited isoproterenol-stimulated cAMP accumulation by 80%, whereas ICI-89406 (3 microM) and ICI-118551 (3 microM) resulted in only partial inhibition (50%). We conclude that both beta 1- and beta 2-adrenoceptors are expressed in initial and terminal IMCD cells in primary culture.
我们研究了培养的大鼠髓质内集合管（IMCD）细胞中表达的β-肾上腺素能受体亚型。在放射性配体结合试验中，[125I]碘氰吲哚洛尔与IMCD细胞膜结合，代表一类单一的结合位点（解离常数 = 96.1 pM，最大结合容量 = 18.2 fmol/mg蛋白质，n = 8）。在竞争研究中，ICI-89406（β1拮抗剂）和ICI-118551（β2拮抗剂）以高亲和力结合，符合双位点模型。异丙肾上腺素增加细胞内3',5'-环磷酸腺苷（cAMP）积累（半数最大有效浓度 = 200 nM）。普萘洛尔完全抑制异丙肾上腺素诱导的cAMP积累[半数最大抑制浓度（IC50） = 270 nM]。ICI-89406和ICI-118551分别使cAMP积累抑制50%（IC50分别为1.5 μM和1.7 μM）。ICI-89406和ICI-118551联合添加产生的曲线与普萘洛尔的曲线无法区分。使用逆转录-聚合酶链反应已证实存在β1和β2肾上腺素能受体mRNA。在初始和终末IMCD细胞中，普萘洛尔（3 μM）抑制异丙肾上腺素刺激的cAMP积累达80%，而ICI-89406（3 μM）和ICI-118551（3 μM）仅导致部分抑制（50%）。我们得出结论，原代培养的初始和终末IMCD细胞中均表达β1和β2肾上腺素能受体。
