Chromaffin Granules in the Rat Adrenal Medulla Release Their Secretory Content in a Particulate Fashion

Enrico Crivellato, Anna Belloni, Beatrice Nico, Gastone G. Nussdorfer, Domenico Ribatti

Research output: Contribution to journalArticlepeer-review


Exocytosis is considered the main route of granule discharge in chromaffin cells. We recently provided ultrastructural evidence suggesting that piecemeal degranulation (PMD) occurs in mouse adrenal chromaffin cells. In the present study, we processed rat adrenal glands for transmission electron microscopy (TEM), and examined chromaffin cells for changes characteristic of PMD. Both adrenaline (A)- and noradrenaline (NA)-storing cells express ultrastructural features suggestive of a slow and particulate mode of granule discharge. In adrenaline-containing cells, some granules present enlarged dimensions accompanied by eroded or dissolved matrices. Likewise, a number of granules in NA-releasing cells show content reduction with variably expanded granule chambers. Dilated, empty granule containers are recognizable in the cytoplasm of both cell types. Characteristically, altered granules and empty containers are seen intermingled with normal, resting granules. In addition, chromaffin granules often show irregular profiles, with budding or tail-like projections of their limiting membranes. Thirty 150-nm-diameter membrane-bound vesicles with a moderately electron-dense or -lucent internal structure are observable in the cytoplasm of both cell types. These vesicles are seen among the granules and some of them are fused with the perigranule membranes in the process of attachment to or budding from the granules. These data add further support to the concept that PMD may be an alternative secretory pathway in adrenal chromaffin cells.

Original languageEnglish
Pages (from-to)204-208
Number of pages5
JournalAnatomical Record - Part A Discoveries in Molecular, Cellular, and Evolutionary Biology
Issue number1
Publication statusPublished - Mar 2004


  • Adrenal chromaffin cells
  • Piecemeal degranulation
  • Rat
  • Transmission electron microscopy

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Anatomy


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