Abstract
The acidic dipeptide N-Acetylaspartylglutamate (NAAG) is thought to be an endogenous ligand of the excitatory amino acid receptor system. Because excitatory amino acids stimulate release of LHRH in vivo, we tested the hypothesis that NAAG might stimulate LHRH release from immortalized LHRH neurons in culture. GN-10 cells, grown to semiconfluence in 24-well plates, were incubated with NAAG, β-NAAG, or glutamate. LHRH secretion was evaluated by enzyme immunoassay. Both NAAG and glutamate elicited LHRH secretion in a dose-dependent manner. 10−9 M NAAG increased LHRH secretion significantly compared to controls (72 ± 45 [SD] vs 13 ± 17 pg/mL, p<0.005), whereas a 100-fold higher concentration of glutamate was required to achieve significant stimulation (46 ± 21 vs 8 ± 11 pg/mL, p<0.005). β-NAAG was inactive at all concentrations (10−13 to 10−4 M). To examine whether the stimulation of LHRH release observed with NAAG could be due to enzymatic cleavage of NAAG into NAA and glutamate, GN-10 cells were incubated for up to 2 hours with NAAG radiolabelled with 3H-Glu, and 3H-NAAG and 3H-glu separated by HPLC. No 3H-glu was detected. We conclude that NAAG is not degraded by GN-10 cells, and that NAAG is a potent stimulus for LHRH release at concentrations at which glutamate is inactive.
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Yanovski, J., Blinder, K., Namboodiri, M. et al. LHRH SECRETION OF IMMORTALIZED HYPOTHALAMIC NEURONS IS STIMULATED BY N-ACETYLASPARTYLGLUTAMATE. Pediatr Res 33 (Suppl 5), S30 (1993). https://doi.org/10.1203/00006450-199305001-00163
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DOI: https://doi.org/10.1203/00006450-199305001-00163