Dayight variations in membrane bound leucyl-2-naphthylamicle hydrolysing activity in rat anterior hypotfaalamus, pituitary and retina

摘要

It is well known that die suprachiasmatic nucleus of the anterior hypothalarnus acts as pacemaker regulating circadiun rhythms in mammals. The daily variations of neuropeptides as well as their receptors depend on this system (Moore 1083). Aminopeptidases play an important role in regulating the activity of brain peptides (Bauer 1982). In this study we investigated membrane bound Ieucyl-2-naphthylamide hydrolysing activity in the anterior hypothalamus, pituitary and retina of adult male rats at six time points of a 12:12h light:dark schedule (light from 7:00 to 19:00 h), in order to analyse its day/ night variation. The fluorometric assay evidenced significant differences between the three regions: in the anterior hypothalamus being higher during die dark period compared with the light period and in the pituitary higher during die light period compared with the dark period. In the retina die levels of this activity showed a higher heterogeneity during die day. Day-night differences in membrane bound leucyl-2-naphdiylamide hydrolysing activity may reflect differences in its susceptible endogenous substrates.