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Isolation of the serotoninergic 5‐HT 4(e) receptor from human heart and comparative analysis of its pharmacological profile in C6‐glial and CHO cell lines
Author(s) -
Mialet Jeanne,
BerqueBestel Isabelle,
Eftekhari Pierre,
Gastineau Monique,
Giner Mireille,
Dahmoune Yamina,
DonzeauGouge Patrick,
Hoebeke Johan,
Langlois Michel,
Sicsic Sames,
Fischmeister Rodolphe,
Lezoualc'h Frank
Publication year - 2000
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0703101
Subject(s) - receptor , biology , chinese hamster ovary cell , agonist , adenylyl cyclase , microbiology and biotechnology , beta 1 adrenergic receptor , receptor expression , medicine , endocrinology , biochemistry
RT–PCR technique was used to clone the human 5‐HT 4(e) receptor (h5‐HT 4(e) ) from heart atrium. We showed that this h5‐HT 4(e) receptor splice variant is restricted to brain and heart atrium. Recombinant h5‐HT 4(e) receptor was stably expressed in CHO and C6‐glial cell lines at 347 and 88 fmol mg −1 protein, respectively. Expression of h5‐HT 4(e) receptors at the cell membrane was confirmed by immunoblotting. The receptor binding profile, determined by competition with [ 3 H]‐GR113808 of a number of 5‐HT 4 ligands, was consistent with that previously reported for other 5‐HT 4 receptor isoforms. Surprisingly, we found that the rank order of potencies ( EC 50 ) of 5‐HT 4 agonists obtained from adenylyl cyclase functional assays was inversely correlated to their rank order of affinities ( K i ) obtained from binding assays. Furthermore, EC 50 values for 5‐HT, renzapride and cisapride were 2 fold lower in C6‐glial cells than in CHO cells. ML10302 and renzapride behaved like partial agonists on the h5‐HT 4(e) receptor. These results are in agreement with the reported low efficacy of the these two compounds on L‐type Ca 2+ currents and myocyte contractility in human atrium. A constitutive activity of the h5‐HT 4(e) receptor was observed in CHO cells in the absence of any 5‐HT 4 ligand and two 5‐HT 4 antagonists, GR113808 and ML10375, behaved as inverse agonists. These data show that the h5‐HT 4(e) receptor has a pharmacological profile which is close to the native h5‐HT 4 receptor in human atrium with a functional potency which is dependent on the cellular context in which the receptor is expressed.British Journal of Pharmacology (2000) 129 , 771–781; doi: 10.1038/sj.bjp.0703101