de Dios I, Rodriguez AI, García-Montero AC, Orfao A, Manso MA. Cholecystokinin regulates glycoprotein membrane composition of rat pancreatic zymogen granules.
BIOCHIMICA ET BIOPHYSICA ACTA 1997;
1326:131-7. [PMID:
9188808 DOI:
10.1016/s0005-2736(97)00015-1]
[Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Lectin-binding studies were performed on rat pancreatic zymogen granules to investigate the alterations in the carbohydrate membrane composition under both chronic CCK stimulation and long-term CCK blockade for 3, 7 and 15 days. By flow cytometry using FITC-WGA--which specifically binds to N-acetylglucosamine and sialic acid--we measured the amount of WGA molecules bound to each individual granule. Parallel studies on pancreatic secretion were also carried out. CCK treatment displayed a differential effect on two zymogen granule subpopulations (Z1 and Z2) identified by flow cytometry on the basis of their light scatter properties: no effects on Z2 zymogen granules were observed in CCK-treated rats, while Z1 granules showed a significant increase in WGA binding at day + 7 which coincides with an increase in protein secretion in response to the hormone. On the contrary, a significant decrease in the amount of WGA receptors was observed in zymogen granule membrane of both the Z1 and Z2 subsets of rats subjected to a long-term CCK blockade. Again, these changes parallel to the reduction observed in protein secretion. Our results suggest that glycoconjugates of zymogen granule membrane involved in CCK-regulated exocytosis contain N-acetylglucosamine and sialic acid residues whose quantities are regulated by CCK.
Collapse