Early expression of a β1-adrenergic receptor and catecholamines in Xenopus oocytes and embryos1The nucleotide sequence reported in this paper has been submitted to EMBL Data Bank with accession number Y09213.1

From a Xenopus stage 11 cDNA library, we have cloned a gene, termed X-β1AR, whose sequence is highly homologous to that of the human β1-adrenergic receptor. As shown by RT-PCR assay, X-β1AR RNA is present in the mature oocyte, decreases after fertilization up to stage 6 and then gradually increases during gastrulation. Binding studies performed with radiolabeled ligands reveal that X-β1AR RNA is translated into the receptor protein. Furthermore, noradrenaline and adrenaline are also detected in oocytes and early embryos. The concomitant presence of β1-adrenergic receptors and catecholamines suggest that this ligand-receptor couple could play a role in the very early stages of embryonic development.