Involvement of metallo-endopeptidase in degradation of luteinizing hormone-releasing hormone by neuronal and glial cells cultured from rat fetal brain.

Luteinizing hormone-releasing hormone (LHRH) was degraded by neuronal and glial cells cultured from fetal rat brain. The degradation of LHRH by neuronal cells was strongly inhibited by a metal chelator. Captopril only inhibited by generation of fragment (1-3) from fragment (1-5). In the presence of captopril, fragment (1-5) accumulated in the highest amount among the N-terminal fragments identified. The initial cleavage of LHRH, as determined by following the loss of the LHRH peak, was strongly inhibited by thiol-blocking reagents, as well as metal chelators. The results with glial cells were almost the same as those seen with neuronal cells. Thus, we propose that a thiol-dependent membrane-bound metallo-endopeptidase plays a major role in the initial stage of degradation of LHRH at the Tyr5-Gly6 bond in both neurons and glia. Angiotensin-converting enzyme is involved in the secondary process of the LHRH degradation in both cells.