A cDNA encoding a functional bradykinin receptor was isolated from a rat uterus library by a clonal selection strategy using Xenopus laevis oocytes to assay for expression of bradykinin responses. The predicted protein is homologous to the seven transmembrane G protein-coupled superfamily of receptors. Bradykinin and its analogs stimulate a Cl current in oocytes expressing the receptor with the rank order of potency: bradykinin Lys-bradykinin > [Tyr8]-bradykinin >> [Phe6Jbradykinin. This is the rank order of potency observed for these compounds in competitive binding assays on soluble receptor from rat uterus. Des-Arg9-bradykinin (10 pAM) elicits no response when applied to oocytes expressing the receptor; thus, the cDNA encodes a B2 type bradykinin receptor. [This8,DPhe7Jbradykinin, where Thi is I3-(2-thienyl)-alanine, is a very weak partial agonist and inhibits the bradykinin-mediated ion flux, suggesting the cDNA encodes a smooth muscle, rather than a neuronal, B2 receptor subtype. Receptor message has a distribution consistent with previous reports of bradykinin function and/or binding in several tissues and is found in rat uterus, vas deferens, kidney, lung, heart, ileum, testis, and brain. Receptor subtypes are a possibility because several tissues contain two or three message species (4.0, 5.7, and 6.5 kilobases). Southern blot highstringency analysis demonstrated that the rat, guinea pig, and human genomes contain a single gene. As bradykinin is a key mediator of pain, knowledge of the primary structure of this receptor will allow a molecular understanding of the receptor and aid the design of antagonists for pain relief.The nonapeptide bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-ProPhe-Arg) is a mediator of pain, inflammation, vascular permeability, smooth muscle tone in vascular and other tissues, and gastrointestinal function (1-5). Bradykinin can serve as a growth factor (2, 6, 7). Bradykinin binds to G proteincoupled receptors that activate phospholipase C or phospholipase A2 and increases synthesis of inositol trisphosphate or arachadonic acid (8-10).Bradykinin receptors have been classified as two major subtypes, B1 and B2 (1). The bradykinin metabolite des-Arg9-bradykinin is a B1 receptor agonist with potency greater than bradykinin, whereas it is inactive at B2 receptors. B2 receptors have been subdivided into two subtypes, a "neuronal" form, which is fully activated by [Thi58,DPhe7]bradykinin, where Thi is 83-(2-thienyl)-alanine, and a "smooth muscle" form, which is weakly activated by [This'8,DPhe7]bradykinin (11,12). Other subtypes of the B2 receptor have also been suggested (13,14).

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To determine the properties of the cAMP-specific, rolipramsensitive phosphodiesterases (cAMP-PDEs) that are expressed in different organs, monoclonal and polyclonal antibodies were raised against different epitopes present in the cAMP-PDE sequences. Of the several antibodies generated against peptides and fusion proteins, one monoclonal and four polyclonal antibodies recognized both the native cAMP-PDEs as well as the denatured proteins on Western immunoblot analysis. An immunoprecipitation assay demonstrated that these antibodies recognized the recombinant rat PDE4A, PDE4B, and PDE4D proteins with different avidity. The polyclonal antibody K118 and the monoclonal M3S1 were most specific for rat PDE4B and PDE4D forms, respectively, whereas the AC55 antiserum displayed the highest affinity for PDE4A forms. This selectivity was confirmed by Western blot analysis using recombinant rat PDE4A, PDE4B, and PDE4D proteins expressed in a heterologous system. These antibodies were used to characterize the cAMP-PDEs expressed in the rat brain. An immunoblot of extract of cortex and cerebellum demonstrated that at least seven different polypeptides specifically cross-reacted with the different antibodies, indicating that multiple cAMP-PDEs are expressed in this tissue. On the basis of cross-reactivity with PDE4D but not PDE4A or PDE4B antibodies, 93-and 105-kDa PDE4D species were detected in the cortex and cerebellum extract. These forms are different from the 68-kDa PDE4D form expressed in endocrine cells after hormonal stimulation. Although the 93-kDa form was recovered in both the soluble and particulate fractions, the 105-kDa polypeptide was mostly particulate in the cortex and cerebellum extracts. PDE4B forms of 90 -87 kDa were recovered in both soluble and particulate compartments of the brain extract. These forms were different from the previously identified PDE4A variants of 110 and 75 kDa. These data demonstrate that the presence of multiple cAMP-PDE genes is translated into cAMP-PDE proteins of different sizes and distinct immunological properties and that multiple variants derived from these cAMP-PDE genes are expressed in different regions of the brain and different subcellular compartments. These immunological tools will be useful to identify different cAMP-PDE forms expressed in organs targeted for pharmacological intervention with PDE4 inhibitors.The high affinity, cAMP-specific phosphodiesterases [type 4 according to the nomenclature proposed by Beavo et al. (1994)] are a class of enzymes with similar kinetic properties that are inhibited by the antidepressant rolipram and structurally related compounds. Although the presence of these forms has long been recognized, their distinctive properties are becoming evident only recently (Conti et al., 1995b). Early attempts to purify these forms have been hampered by their low abundance and instability (Conti and Swinnen, 1990). The molecular mass attributed to this group of enzymes ranges between 29 and 89 kDa (Conti and Swinnen, 1990). The definition of th...

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