Binding kinetics and sequencing of hepatic alpha1-adrenergic receptors in two marine teleosts, mackerel (Scomber scombrus) and anchovy (Engraulis encrasicolus).
Liver alpha(1)-adrenoceptors (ARs) are demonstrated, or at least hypothesized, in freshwater and brackish-water teleosts, whereas no data are available for marine teleosts. This study evaluates the presence of alpha(1)-ARs in the liver of two marine teleosts, the anchovy Engraulis encrasicolus and the mackerel Scomber scombrus, and examines on a broad scale the possibility that habitats posing different challenges also influence phenotypic trait selection. Binding assays were performed also on liver membranes from the carp Cyprinus carpio as a direct comparison with a freshwater species. Scatchard analysis of [(3)H]prazosin binding to purified liver membranes from anchovy, mackerel and carp resulted in K(d) values of 1.51+/-0.085, 1.26+/-0.098, and 2.61+/-0.22 nM, and B(max) values of 87.4+/-9.12, 77+/-8.29, and 115.22+/-3.31 fmol/mg protein, respectively. Thus, alpha(1)-ARs of the two marine teleosts showed higher [(3)H]prazosin affinity compared with those of the freshwater/brackish-water fish studied thus far, whereas the number of liver binding sites did not differ significantly from that of carp, eel or trout. A preliminary phylogeny based on amino acid sequence analysis indicated the presence of at least an alpha(1A)-AR in mackerel and an alpha(1D)-AR in both anchovy and mackerel. This is the first indication of alpha(1)-AR subtypes in any marine species, but further studies are needed to ascertain the physiological role of these alpha(1)-ARs in these two marine species.
Fabbri
Elena
E
Interdepartment Centre for Environmental Science Research, University of Bologna, Ravenna, Italy. elena.fabbri@unibo.it
Chen
Xi
X
Capuzzo
Antonio
A
Moon
Thomas W
TW
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D003001:Cloning, Molecular; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008969:Molecular Sequence Data; D010473:Perciformes / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D011224:Prazosin / Q000494:pharmacology; D012313:RNA / Q000737:chemistry / Q000235:genetics; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012623:Seawater; D016415:Sequence Alignment
D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D012313:RNA; D011224:Prazosin