Fine ultrastructure of chromaffin granules in rat adrenal medulla indicative of a vesicle-mediated secretory process

E. Crivellato, D. Guidolin, B. Nico, G. G. Nussdorfer, D. Ribatti

Research output: Contribution to journalArticlepeer-review


Observation by transmission electron microscopy, coupled with morphometric analysis and estimation procedure, revealed unique ultrastructural features in 25.94% of noradrenaline (NA)-containing granules and 16.85% of adrenaline (A)-containing granules in the rat adrenal medulla. These consisted of evaginations of the granule limiting membrane to form budding structures having different morphology and extension. In 14.8% of NA granules and 12.0% of A granules, outpouches were relatively short, looked like small blebs emerging from the granule surface and generally contained electron-dense material. A proportion of 11.2% of NA granules and 4.9% of A granules revealed the most striking ultrastructural features. These secretory organelles presented thin, elongated, tail-like or stem-like appendages, which were variably filled by chromaffin substance and terminated with spherical expansions of different electron density. A cohort of vesicles of variable size (30-150 nm in diameter) and content was found either close to them or in the intergranular cytosol. Examination of adrenal medullary cells fixed by zinc iodide-osmium tetroxide (ZIO) revealed fine electron dense precipitates in chromaffin granules, budding structures as well as cytoplasmic vesicles. These data indicate that a common constituent is revealed by the ZIO histochemical reaction in chromaffin cells. As catecholic compounds are the main tissue targets of ZIO complexes, catecholamines are good candidates to be responsible for the observed ZIO reactivity. This study adds further to the hypothesis that release of secretory material from chromamn granules may be accomplished by a vesiclular transport mechanism typical of piecemeal degranulation.

Original languageEnglish
Pages (from-to)79-86
Number of pages8
JournalAnatomy and Embryology
Issue number1
Publication statusPublished - Jan 2006


  • Chromaffin granules
  • Osmium-zinc iodide
  • Piecemeal degranulation
  • Rat
  • Ultrastructure

ASJC Scopus subject areas

  • Anatomy
  • Developmental Biology
  • Cell Biology
  • Embryology


Dive into the research topics of 'Fine ultrastructure of chromaffin granules in rat adrenal medulla indicative of a vesicle-mediated secretory process'. Together they form a unique fingerprint.

Cite this