Decreased mRNA levels for exocytotic proteins in the pituitary of aged rats.
Several protein components that are involved in the molecular regulation of transmitter release have been identified in neuronal, neuroendocrine and endocrine tissues. The expression of VAMP-2 (vesicle-associated membrane protein), munc-18 (mammalian homologue of unc-18) and SNAP-25 (synaptosomal-associated protein of 25 kDa) mRNA was studied in the rat anterior and intermediate pituitary gland of adult (2 months) and old (24 months) rats using in situ hybridization. In the pituitary anterior lobe of aged rats, there was a significant decrease in VAMP-2 (33%), munc-18 (17%) and SNAP-25 (20%) mRNA as compared to adult rats. In the intermediate lobe, there was a significant decrease in VAMP-2 (48%) and SNAP-25 (32%) mRNA of aged rats, whereas munc-18 mRNA levels were not significantly changed. Pituitaries from aged rats showed an increase in size which was paralleled by a significant decrease in the number of cells per unit area in the intermediate lobe, whereas the number was unaltered in the anterior lobe. The results suggest a genuine decrease in mRNA for exocytotic protein mRNA in the anterior pituitary, but that part of the decrease in the expression of VAMP-2 and SNAP-25 mRNA in the intermediate lobe can be explained by a decreased number of cells per unit area. The decline in anterior pituitary hormone secretion reported in aged rats appears to be parallelled by a down-regulation in mRNA levels for several proteins involved in the molecular regulation of exocytosis.
Jacobsson
G
G
Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
Pelto-Huikko
M
M
Meister
B
B
D000375:Aging / Q000378:metabolism*; D000818:Animals; D005089:Exocytosis / Q000502:physiology*; D017403:In Situ Hybridization; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D010902:Pituitary Gland / Q000378:metabolism* / Q000473:pathology; D010903:Pituitary Gland, Anterior / Q000378:metabolism / Q000473:pathology; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D050683:R-SNARE Proteins; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D050825:Synaptosomal-Associated Protein 25; D033921:Vesicular Transport Proteins
D008565:Membrane Proteins; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D050683:R-SNARE Proteins; D012333:RNA, Messenger; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D033921:Vesicular Transport Proteins