SYNTHESIS OF C-TYPE NATRIURETIC PEPTIDE (CNP) BY IMMORTALIZED LHRH CELLS

Former studies have indicated an influence of natriuretic peptides on LHRH secretion. In this report we demonstrate local synthesis of CNP i n immortalized LHRH neurons (GT1-7 cells). Using reverse transcription -polymerase chain reaction and RNase protection assays a transcript fo r the CNP precursor was identified in these cells. Immunocytochemical data revealed the presence of the peptide CNP in GT1 cells, using a sp ecific polyclonal antiserum against CNP. Electron microscopic immunohi stochemical investigations also showed the strongest CNP-immunoreactiv ity in some small vesicles, providing initial evidence for the potenti al secretion of this peptide by immortalized LHRH neurons. Subsequent experiments demonstrated also that CNP elevates LHRH production in sta tic cultures of GT1 cells. These data show for the first time the co-p roduction of the functionally relevant natriuretic peptide, CNP, by im mortalized LHRH neurons. Together with the recent demonstration of CNP receptor expression by these cells, we suggest that CNP may represent a novel autocrine regulator of LHRH neuronal activity. It remains to be elucidated, however, to what extent CNP expression in immortalized LHRH neurons reflects a co-localization in situ of CNP and LHRH peptid es.