Radioimmunocytochemical distribution of neutral endopeptidase (enkephalinase E.C.3.4.24.11) at the ultrastructural level in the rat median eminence.
Neutral endopeptidase (E.C.3.4.24.11) was visualized at the ultrastructural level in the external zone of the rat median eminence by using 125I-labelled IgG of a monoclonal serum. A precise analysis of the localization of the immunolabelling, which appears in the form of individual stray silver grains, was undertaken. Among the 1,045 grains counted, 82% were localized over membrane appositions involving nerve endings only and nerve endings plus tanycytes. The difference between the real and a randomly generated population of grains was statistically significant. Our results provide morphological arguments in support of the view of a paracrine action of neuropeptides present in the median eminence especially enkephalins but possibly, substance P, angiotensin, cholecystokinin and neurotensin. These neuropeptides are known to be inactivated by neutral endopeptidase. The action of these peptides may be exerted on nerve endings (autocrine or paracrine) but an intervention on tanycytes cannot be excluded.
Vandenbulcke
F
F
Unité 156 INSERM, Lille, France.
Pollard
H
H
Mitchell
V
V
Beauvillain
J C
JC
D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D001345:Autoradiography; D002766:Cholecystokinin / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D008473:Median Eminence / Q000033:anatomy & histology / Q000201:enzymology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D015260:Neprilysin / Q000276:immunology / Q000378:metabolism*; D009411:Nerve Endings / Q000648:ultrastructure; D009496:Neurotensin / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D016622:Silver Staining; D013373:Substance P / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000804:Angiotensin II; D013373:Substance P; D009496:Neurotensin; D002766:Cholecystokinin; D015260:Neprilysin