Mast cells in damaged striated muscle of lymph heart in the adult frog: An ultrastructural, immunocytochemical, and auroradiographic study

Аннотация

We have studied mast-cell (MC) activation in the border area of mechanically damaged muscle in Rana temporaria lymph heart for 1 week after the surgery. Twenty-four hours after surgery, the cytoplasm of resident and circulating MCs contained degranulation channels discharging via compound exocytosis. Rare cases of single membrane-free expelled granules were revealed in the space limited with the plasma membrane of a resident MC and surrounding basal lamina. During the first week after the surgery the ultrastructural changes in many secretory granules of activated MCs concerned the granule swelling, reduced amount of the electron-dense component and pronounced loosing of their matrix. It is noteworthy that unaltered and altered granules are located close to empty degranulation channels frequently penetrated MC cytoplasm from the surface to centrally localized nucleus. Immunocytochemical MC labeling with antibodies to histamine revealed that gold particles were located under both altered and unaltered granules. In altered granules, gold particles were arranged above a preserved electron-dense part, whereas a loosened matrix, as a rule, was not labeled. Ultrastructural signs of secretory granule formation in the MC cytoplasm were disclosed to the end of the first week after surgery. Electron-microscopic autoradiography revealed that replicative and transcriptional activity of an MC in the border area was not prominent during all the periods after the surgery. Mitotic MCs were not observed. Occasionally, MCs dying via necrosis were encountered. These observations show that MCs stimulated by mechanical damage of the lymph heart secrete various preformed mediators, histamine in particular. The early response of MCs in the border area is evidence that activated MCs play a key role in the initiation of inflammation in the damaged cross-striated muscle of the lymph heart.