Glucocorticoids regulate L-fucose glycoconjugates in rat pancreatic zymogen granules.
Lectin-binding studies were performed on rat pancreatic zymogen granules to investigate the influence of glucocorticoid levels on saccharide membrane composition. The following animal groups were used: (1) control rats; (2) rats treated with hydrocortisone (1, 10 and 25 mg/kg/day) for 1, 3 and 8 days; (3) postadrenalectomized rats at days +1, +3 and +8; and (4) adrenalectomized rats receiving hydrocortisone therapy (10 mg/kg/day) for 8 days. By flow cytometry, fluoresceinated (FITC) lectins were used to measure the amount of Concanavalin A (Con A) (specific for D-mannose), wheat germ agglutinin (WGA) (specific for N-acetyl-D-glucosamine) and sialic acids and Tetragonolobus purpureus (TP) (specific for L-fucose) bound to individual zymogen granules from two subpopulations, Z1 and Z2, identified on the basis of their forward and side scatter properties. The molar ratio of the different FITC-lectins revealed significant differences in the glycoconjugate composition of Z1 and Z2 granules, the Z1 granules showing higher ratios of N-acetyl-D-glucosamine:L-fucose and N-acetyl-D-glucosamine:D-mannose, both in control, adrenalectomized and hydrocortisone-treated rats. It was also observed that N-acetyl-D-glucosamine and/or sialic acids were more abundant than L-fucose and D-mannose in the zymogen granule membrane. Z1 and Z2 granules had different glycosylation patterns. Neither adrenalectomy nor hydrocortisone treatments varied the Con A binding to zymogen granules. An increase in WGA binding was only induced by administration of very high doses of hydrocortisone (25 mg/kg/day) for 8 days, an effect not directly related to glucocorticoids. In contrast, a correlation between the FITC-TP labelling and glucocorticoid levels can be established, so that, in a time-dose dependent way, an increase was observed in zymogen granules of rats treated with hydrocortisone while a decreased TP binding was found in adrenalectomized rats-an effect which was reversed with hydrocortisone therapy. Therefore, glucocorticoids exert a direct influence on the saccharide composition of rat pancreatic zymogen granules, regulating the amount of L-fucose glycoconjugates, with Z2 granules more sensitive than Z1 ones.
García-Montero
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Department of Physiology and Pharmacology, Miguel de Unamuno Campus, University of Salamanca, Spain.
Manso
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MA
Rodriguez
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AI
Orfao
A
A
de Dios
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I
D000117:Acetylglucosamine / Q000378:metabolism; D000311:Adrenal Glands / Q000502:physiology; D000315:Adrenalectomy; D000818:Animals; D003594:Cytoplasmic Granules / Q000378:metabolism*; D004792:Enzyme Precursors / Q000378:metabolism*; D005434:Flow Cytometry; D005643:Fucose / Q000378:metabolism*; D005938:Glucocorticoids / Q000494:pharmacology*; D006001:Glycoconjugates / Q000378:metabolism*; D006031:Glycosylation; D006854:Hydrocortisone / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D037102:Lectins / Q000378:metabolism; D008297:Male; D010179:Pancreas / Q000201:enzymology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D004792:Enzyme Precursors; D005938:Glucocorticoids; D006001:Glycoconjugates; D037102:Lectins; D005643:Fucose; D000117:Acetylglucosamine; D006854:Hydrocortisone