title: Rapidly induced modulation of beta-N-acetylglucosaminidase activity in pancreatic islets.
abstract: The aim of this work was to determine the possible rapid modulatory effect of glucose on the activity of pancreatic islet lysosomal enzymes. For this purpose, beta-N-acetylglucosaminidase and beta-galactosidase activities were measured in homogenates of isolated rat islets after a 5, 15, 30 or 60-min exposure to either 3.3 or 16.6 mM glucose. The enzyme activities were determined spectrofluorometrically by means of their respective 4-methylumbelliferyl derivatives as substrates. beta-N-acetylglucosaminidase activity measured in freshly isolated non-incubated islets was 5.482 +/- 0.281 mumol/mg protein/h at 37 degrees C. In islets incubated with 3.3 mM glucose, this activity dropped significantly after 5 min and remained almost constant until the end of the incubation period. In islets incubated with 16.6 mM glucose, beta-N-acetylglucosaminidase activity also decreased significantly at 5 min, and attained its lowest value after 15 min of incubation. After this interval, the activity began to recover and thereafter gained a value close to that measured in non-incubated islets by 60 minutes' time. Despite this ultimate recovery, the enzyme activities measured were significantly lower than those found in islets incubated with 3.3 mM glucose. beta-galactose activity in freshly isolated non-incubated islets was 0.515 +/- 0.094 mumol/mg protein/h at 37 degrees C. This value remained almost unchanged throughout the incubation period in the presence of either 3.3 or 16.6 mM glucose. These results show that beta-N-acetylglucosaminidase activity, a lysosomal hydrolase of pancreatic rat islets,--and only this enzyme--is modulated by glucose.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: CENEXA-Centro de Endocrinologia Experimental y Aplicada (UNLP-CONICET), La Plata, Argentina.
authors.forename: M I
authors.initials: MI
authors.lastname: Borelli
authors.forename: V
authors.initials: V
authors.lastname: Alvarez
authors.forename: E
authors.initials: E
authors.lastname: de Gagliardino
authors.forename: R
authors.initials: R
authors.lastname: Couso
authors.forename: J J
authors.initials: JJ
authors.lastname: Gagliardino
mesh_terms: D000118:Acetylglucosaminidase / Q000378:metabolism*; D000818:Animals; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D007700:Kinetics; D008247:Lysosomes / Q000201:enzymology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D007328:Insulin; D001616:beta-Galactosidase; D000118:Acetylglucosaminidase; D005947:Glucose