Post-natal maturation of acinar cells of the guinea pig pancreas: an ultrastructural morphometric study.
The morphological maturation of the acinar cells of the guinea pig pancreas during post-natal development was characterized morphometrically by determining the intracytoplasmic accumulation of rough endoplasmic reticulum (RER) and zymogen granules. The following results were obtained for the period analysed, i.e., from 2 to 70 days of post-natal life: (a) the acinar cell volume increased by 210% (P < 0.01); (b) the mostly cisternal RER occupied more than 30% of the cytoplasm at any age studied and their total volume and surface in the cell were increased by 300 and 534% (P < 0.01), respectively; (c) maturation in the morphological pattern of the RER was observed; (d) the mean number of zymogen granules per cell increased from 261 at 2 days to 422 at 70 days (P < 0.01), while their mean diameter increased from 0.52 to 0.94 micron (P < 0.01) during the same period; (e) these increases in granule number and size were responsible for a 500% (P < 0.01) increase in total volume from 2 to 70 days and for a 304% increase (P < 0.01) in total surface from 2 to 35 days; (f) the RER and the zymogen granules together occupied 44, 54, 55 and 57% of the cytoplasm at 2, 14, 35 and 70 days of age, respectively. We conclude that although the pancreatic acinar cells of the guinea pig are morphologically well differentiated at 2 days of age, with the cytoplasm already showing a large amount of RER and zymogen granules, they are still immature. Morphological maturation of the acinar cell occurs during the first months of post-natal life and is characterized by a substantial gain in cell volume and intracytoplasmic accumulation of RER and zymogen granules, which significantly increase of both their absolute volume and total surface, with a higher growth rate being observed during the period from 2 to 14 days of post-natal life.
Departamento de Ciências Biológicas-Histologia, Faculdade de Odontologia de Bauru, Universidade de São Paulo, Al. Dr. Octávio Pinheiro Brisola 9-75, CEP-17.012-901, Bauru, SP, Brazil. gfassis@fob.usp.br
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D000818:Animals; D018870:Endoplasmic Reticulum, Rough / Q000648:ultrastructure; D004792:Enzyme Precursors / Q000378:metabolism; D006168:Guinea Pigs / Q000033:anatomy & histology*; D008297:Male; D010179:Pancreas / Q000166:cytology* / Q000648:ultrastructure*; D022142:Secretory Vesicles / Q000648:ultrastructure
D004792:Enzyme Precursors