NATRIURETIC PEPTIDES STIMULATE CYCLIC-GMP PRODUCTION IN AN IMMORTALIZED LHRH NEURONAL CELL-LINE

The role of cyclic 3',5'-guanosine monophosphate (cGMP) as a second me ssenger in LHRH neurons is not well understood. Recent studies involvi ng nitric oxide, a direct activator of soluble guanylate cyclase (GC), have implicated cGMP in the regulation of LHRH secretion both in vivo and in vitro. Evidence for the membrane-bound form of GC in LHRH neur ons has thus far not been reported. In polymerase chain reaction scree ning of various cell lines for the natriuretic peptide receptors-which represent GCs-we identified both GC-A and GC-B cDNAs by southern blot hybridization in reverse transcribed and amplified extracts of the GT 1-7 cell line, an immortalized LHRH neuronal cell line. Subsequent exp eriments demonstrated that all of the natriuretic peptides elevated cG MP production with a rank order of potency: CNP > ANP > BNP. Time cour se studies revealed a rapid intracellular accumulation of cGMP followi ng exposure to CNP with a peak at 2.5 min. CNP was some 200-fold more potent than the NO donor, sodium nitroprusside, in stimulating cGMP ac cumulation in these cells. These data show for the first time the pres ence of functional mGCs on LHRH cells, and suggest that the natriureti c peptides may also participate in the regulation of LHRH activity.