Changes in the content and distribution of sialic acid on the basal surface of isoproterenol-stimulated mouse parotid acinar cells.
The presence, distribution and content of sialic acid on the cell surface in collagenase-dispersed acini obtained both from unstimulated as well as from in vivo isoproterenol-stimulated mouse parotid have been studied. To this end, sialic acid residues have been qualitatively and quantitatively analyzed by 1) cytochemical labeling by wheat germ agglutinin (WGA), 2) biochemical procedures and 3) isotopic labeling by [3H]WGA (WGA-N-[acetyl-3H]-acetylated). Electron microscopy revealed striking differences in the binding of ferritin-conjugated WGA at the basal, lateral and apical cell surface. Unstimulated acinar cells showed a heavy patch-distributed binding of ferritin-conjugate on the basal cell surface while it was homogeneous and very scarce on the lateral one and absent on the apical cell surface. During the first few hours after isoproterenol, the WGA binding sites at the basal cell surface became homogeneously distributed. This fact was coincident with a loss of about 60 to 70% both in the content of neuraminidase-releasable sialic acid and in the binding of [3H]WGA to the acinar surface. These findings suggest that the release of sialic acid as free residues, which has been involved in the isoproterenol-triggered cell proliferation-inducing mechanism in the mouse parotid, would occur at the glycocalyx corresponding to the basal plasma membrane of the acinar cells.
Department of Cell Biology and Genetics, Faculty of Medicine, University of Chile, Santiago.
M
M
Julieta González
N
N
Galanti
R O
RO
López Solís
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D019158:N-Acetylneuraminic Acid; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D012794:Sialic Acids / Q000378:metabolism*; D014909:Wheat Germ Agglutinins / Q000378:metabolism
D008565:Membrane Proteins; D012794:Sialic Acids; D014909:Wheat Germ Agglutinins; D019158:N-Acetylneuraminic Acid; D007545:Isoproterenol