Piecemeal degranulation as a general secretory mechanism?
In this article we review the ultrastructural findings, functional aspects, and biological significance of piecemeal degranulation (PMD), a unique secretory pathway that has been described in basophils, mast cells, and eosinophils. Recent ultrastructural data suggestive of PMD in enteroendocrine cells of the gastrointestinal tract and chromaffin cells of the adrenal medulla are also presented and discussed. Further research on PMD in secretory cells of the endocrine and exocrine glands, as well as in neurons, is recommended, since the current data indicate that PMD has a broader spectrum of expression than was hitherto reported. The identification of the PMD phenotype in different cell types (e.g., basophils, mast cells, eosinophils, enteroendocrine cells, and adrenal chromaffin cells) suggests that PMD is a unique degranulation model for paracrine and endocrine secretion. Further investigation will clarify whether PMD can be considered as a general mechanism for the slow release of bioactive stored materials by granulated secretory cells.
Crivellato
Enrico
E
Department of Medical and Morphological Research, University of Udine School of Medicine, Udine, Italy.
Nico
Beatrice
B
Mallardi
Franco
F
Beltrami
Carlo Alberto
CA
Ribatti
Domenico
D
D000818:Animals; D001491:Basophils / Q000502:physiology; D015550:Cell Degranulation / Q000502:physiology*; D004702:Endocrine Glands / Q000166:cytology* / Q000502:physiology* / Q000648:ultrastructure; D004804:Eosinophils / Q000502:physiology; D006801:Humans; D008407:Mast Cells / Q000502:physiology