Meeting Abstract
53.3 Jan. 6 Endothelin from the killifish, Fundulus heteroclitus HYNDMAN, Kelly A*; EVANS, David H; University of Florida, Gainesville; Mount Desert Biological Laboratory, Salisbury Cove ME khyndman@zoo.ufl.edu
Endothelin-1 (ET-1) is a vasoactive, paracrine peptide found in all vertebrates. It is produced in a variety of cells including endothelial, vascular smooth muscle, and transporting epithelial cells such as kidney tubules. In mammals, ET-1 is translated as a 203 amino acid (AA) preprohormone, termed preproendotheiln (PPET), and it undergoes two cleavage events to produce the active 21 AA ET. Endothelin�s functions are mediated via two G-protein coupled receptors (GPCR) in mammals, ETA and ETB1, and by a third GPCR in non-mammalian vertebrates, ETB2. Although ET-1 is traditionally viewed as a cardiovascular paracrine, recent studies suggest that ET plays a role in ion regulation in mammals and fishes. Electrophysiological studies from our lab have suggested that ET-1 inhibits net chloride transport in the opercular epithelium (a model for the sea water teleost gill) of the euryhaline killifish (Fundulus heteroclitus). Thus, we hypothesize that ET-1 may be a modulator of ion balance in euryhaline fishes. To explore this, we have cloned the cDNA encoding ET-1 from the killifish. We have found two ET-1 transcripts, and have designated them kET-1a and kET-1b. kET-1a contains 940 bp with a predicted open reading frame (ORF) of 483 bp, translating into a 161 AA PPET. kET-1b contains 935 bp with a predicted ORF of 429 bp, translating into a PPET of only 143 AA. The predicted active form (21 AA) of the killifish ET-1 is 100% identical between kET-1a and kET-1b, and they share 81% identity with human ET-1. In addition, tissue distribution and effects of environmental salinity on the mRNA expression of the two kET-1 transcripts were determined. These studies provide a better understanding of how the ET signaling axis plays a role in ion balance in euryhaline fishes.
