Characterization of immunoreactive substance P and neurotensin in the goldfish retina

Extracts of goldfish retina and brain were analysed by high-pressure liquid chromatography and radioimmunoassays for neurotensin (NT), substance P (SP) and related peptides. Two major peaks of immunoreactive NT were observed, both more hydrophilic than mammalian NT. Although these two forms reacted equally well with two antisera towards the biologically active carboxyl terminal region of NT, they were not recognized by an amino terminal antiserum, nor by antisera toward the related peptides, LANT-6 and xenopsin. Retinal immunoreactive SP eluted as one major peak which may represent the teleost equivalent of mammalian SP; region-specific antisera indicated phylogenetic conservation of the carboxyl terminal region. A more hydrophilic immunoreactive form was found only in brain, and two more hydrophobic forms found in both tissues were relatively more abundant in retina than in brain. The concentrations and molecular forms of these peptides were unchanged after either 48 hr of light adaptation or 48 hr of dark adaptation.