title: Parallel increase in secretory activity between N-glycosylated and nonglycosylated α-amylase without protein synthesis after short-term β-adrenergic receptor activation in isolated rat parotid acinar cells.
abstract: OBJECTIVE
  To investigate comparisons of the secretory activity between N-glycosylated and nonglycosylated α-amylase, and α-amylase synthetic activity, after β-adrenergic receptor activation in rat parotid acinar cells in vitro.
  
  
  METHODS
  Rat parotid acinar cells were incubated in the presence or absence of (-)-isoproterenol. For β-adrenergic blocking experiments, acinar cells were pretreated with (±)-propranolol prior to adding agonist. After the time indicated, the "released amylase" and "total amylase" were obtained. Western blotting was applied to identify and quantify the N-glycosylated and nonglycosylated α-amylase. Amylase activity was also measured.
  
  
  RESULTS
  The potent β-adrenergic agonist (-)-isoproterenol induced a dramatic increase (2-3-fold) of α-amylase secretion for 30 minutes (p < 0.05 vs. control), while the effect was completely abolished when cells were pretreated with (±)-propranolol for 15 minutes. Moreover, the N-glycosylated level of released and total amylase among groups was measured accordingly. Our data showed the N-glycosylated level ratios (released amylase/total amylase) did not differ among groups, which indicated that the N-glycosylated form of α-amylase was not secreted more easily than the nonglycosylated one after stimulation. Interestingly, the total amylase concentration remained unchanged after stimulation within 30 minutes, which might indicate no α-amylase synthesized within the time indicated.
  
  
  CONCLUSIONS
  Our findings suggest a parallel increase in secretory activity between N-glycosylated and nonglycosylated α-amylase after β-adrenergic receptor activation. There seems to be a dissociation of α-amylase synthesis from secretion within 30 minutes.
authors: Long-hui
authors: LH
authors: Chen
authors: Ze-min
authors: ZM
authors: Yang
authors: Wei-wen
authors: WW
authors: Chen
mesh_terms: D061354:Acinar Cells / Q000187:drug effects / Q000473:pathology; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage; D000818:Animals; D006031:Glycosylation / Q000187:drug effects*; D006801:Humans; D007545:Isoproterenol / Q000008:administration & dosage; D010306:Parotid Gland / Q000187:drug effects* / Q000473:pathology; D014176:Protein Biosynthesis; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000096:biosynthesis / Q000235:genetics*; D000516:alpha-Amylases / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D000516:alpha-Amylases; D007545:Isoproterenol