Urotensin I- and CRF-like peptides in Catostomus commersoni brain and pituitary--HPLC and RIA characterization.

Two distinct neuronal systems, containing urotensin I-like immunoreactivity (UI-LI) and CRF-LI respectively, have previously been demonstrated immunocytochemically in the brain and pituitary of the teleost Catostomus commersoni. In the present studies, we used HPLC followed by UI- and CRF-RIA to further characterize these UI- and CRF-LI substances. HPLC of Catostomus brain extracts (including extracts modified by dilute H2O2 oxidation or dilute acid cleavage) suggests that the major form of brain UI-LI is very likely identical to the previously characterized urophysial UI; the small amount of pituitary UI-LI is not yet fully characterized. The behavior of brain CRF-LI on reversed phase (RP) extraction suggests that it may exist largely in precursor form. Pituitary CRF-LI, however, behaved as expected for a peptide on RP extraction, and eluted from HPLC as essentially a single (though somewhat broad) peak. The HPLC behavior of pituitary CRF-LI, and its crossreactivity with various CRF antisera, suggest that it represents authentic fish CRF, apparently similar to (but not identical with) human/rat CRF.