LOCAL SYNTHESIS OF NATRIURETIC PEPTIDES IN THE EEL INTESTINE

The intestine is a major osmoregulatory organ in euryhaline fishes whi ch allows them to survive in the sea, and natriuretic peptides have be en implicated in regulation of transmural transport. Atrial (ANP) and ventricular natriuretic peptide (VNP) were identified in eel intestine . tine. Elution profiles of ANP and VNP from high-performance liquid c hromatography (HPLC) were determined by radioimmunoassay using highly specific antisera. Elution times of immunoreactive ANP and VNP in HPLC were identical to those of authentic peptide standards and were consi stent with the relative molecular masses of these peptides. Tissue loc alization of ANP and VNP was accomplished by fluorescence immunohistoc hemistry. Immunoreactive cells were observed in the epithelium of ante rior, middle, and posterior regions of intestine. Reverse transcriptio n of mRNA isolated from intestine and subsequent polymerase chain reac tion amplification yielded appropriate-size products consistent with A MP and VNP expression. Together, these data show that natriuretic pept ides are synthesized locally in eel intestine, rather than trapped fro m the circulation. (C) 1997 Academic Press.