Meeting Abstract
P1.218 Friday, Jan. 4 Multiple AVT receptors in teleost fish: Identification and tissue distribution of two distinct V2-type AVT receptor cDNAs in Amargosa pupfish WALTI, K.A.*; SANDERS, K.E.; LEMA, S.C.; CalPoly, San Luis Obispo; CalPoly, San Luis Obispo; CalPoly, San Luis Obispo slema@calpoly.edu
The neurohypophysial hormone arginine vasotocin (AVT) and its mammalian homolog arginine vasopressin (AVP) regulate hydromineral balance and social behaviors in vertebrates. In mammals, the actions of AVP are mediated by three types of receptors: V1a, V1b and V2. Previously, our laboratory identified multiple V1a-type receptors (V1a1 and V1a2) and the first teleost V2-type receptor from the Amargosa pupfish (Cyprinodon nevadensis amargosae). The evolution of these two V1a-type receptors and a V2-type AVT receptor has since been confirmed in other teleost species. Here, we used degenerate primer PCR to amplify and sequence a 551-bp nucleotide partial cDNA encoding a fourth AVT receptor from Amargosa pupfish. Alignment of the deduced amino acid sequence of this partial cDNA against previously described nonapeptide receptors revealed only 55.7% and 60.2% identity, respectively, to the V1a1 and V1a2 AVT receptors of Amargosa pupfish. Rather, this new cDNA encodes a deduced receptor with highest sequence identity to a clade of V2-type receptors comprised of avian V2-type receptors (63.4-63.6% identity) and a newly described V2-type receptor V2b from pufferfish (75.4%), stickleback (74.9%) and zebrafish (68.3%). RT-PCR showed that v2b mRNAs encoding this receptor are present at highest relative levels in the brain, heart and testis of pupfish. This contrasts with the distribution of v2a receptor gene transcripts, which are at greatest abundance in the pituitary gland, gills, heart, kidney and ovary. Although the functional role of this V2b V2-type AVT receptor remains unclear at present, the evolutionary diversity of AVT receptors in fishes suggests a high potential for the evolution of AVT action via receptor-specific function.
