Molecular cloning of three types of arginine vasotocin receptor in the newt, Cynops pyrrhogaster

Three types of cDNA encoding the arginine vasotocin (AVT) receptors from the newt, Cynops pyrrhogaster were cloned and the gene expression of each receptor analyzed in the organs and tissues of the newt. The deduced amino acid sequence of one type of AVT receptor, consisting of 418 amino acid residues, showed a high degree of sequence identity with the mammalian arginine vasopressin (AVP) V1a receptors (61–68%). The second type of cDNA, encoding an amino acid sequence consisting of 367 amino acid residues, exhibited a relatively high sequence identity with mammalian AVP V2 receptors (50–51%). The third cDNA, encoding a sequence of 415 amino acid residues, possessed high sequence identity with mammalian AVP V3/V1b receptors (59–63%). Phylogenetic analysis revealed that the first, second and third types of receptor were close to mammalian AVP V1a, V2 and V3/V1b receptors, respectively, and RT-PCR using gene specific primers for each type of receptor indicated that the first and second types of receptor mRNA were expressed in various organs and tissues, including the circulatory, osmoregulatory, and reproductive organs of both male and female newts. In contrast, mRNA expression of the third cDNA was mainly detected in the brain and pituitary, and its expression pattern was distinctly different from that of the other two. We suggest that the first, second and third types of newt AVT receptor obtained in the present study are counterparts of mammalian AVP V1a, V2 and V3/V1b receptors, respectively.