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Parasympathetically-mediated swelling of mast cell granules during feeding
A M Rothschild1, E L Gomes, M A Rossi
1Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
Abstract:
Mesentery mast cells have been observed to swell and to spontaneously return to their original size following feeding of 12-h fasted rats. This effect may be controlled by parasympathetic efferent nerve impulses, since it is inhibited by atropine. It was reproduced in vitro in isolated rat peritoneal fluid mast cells exposed for 30s to 10(-8)-10(-11) M acetylcholine. When examined under the electron microscope, mast cell average granule diameters had increased by 29% (p less than 0.001) following treatment. Swollen granules did not leave (exocytose) acetylcholine-treated mast cells. They gradually and spontaneously returned to their original size. This recovery only differed from that occurring in the fed rat by its greater speed.
Insights
Feeding causes mast cells in rat mesentery to swell and recover size, potentially via parasympathetic nerves. Acetylcholine in vitro also swells mast cell granules, which then return to normal size.
Area of Science:
- Physiology
- Cell Biology
Background:
- Mesentery mast cells exhibit swelling and spontaneous size recovery after feeding in fasted rats.
- This phenomenon is suggested to be regulated by parasympathetic efferent nerve impulses, as indicated by inhibition with atropine.
Purpose of the Study:
- To investigate the effect of acetylcholine on mast cell granule size in vitro.
- To determine if acetylcholine induces mast cell swelling and to characterize the recovery process.
Main Methods:
- Isolated rat peritoneal mast cells were exposed to varying concentrations of acetylcholine (10^-8 to 10^-11 M) for 30 seconds.
- Electron microscopy was used to measure mast cell granule diameters before and after acetylcholine treatment.
- The recovery of granule size was observed over time.
Main Results:
- Acetylcholine exposure caused a significant increase in mast cell average granule diameter by 29% (p < 0.001).
- Swollen granules did not undergo exocytosis (release) from the mast cells.
- Mast cells gradually and spontaneously returned to their original granule size, with a faster recovery than observed in fed rats.
Conclusions:
- Acetylcholine directly induces mast cell granule swelling in vitro, mimicking a post-feeding response.
- Mast cell degranulation (exocytosis) is not the mechanism behind this swelling and recovery.
- The findings support a role for parasympathetic stimulation in modulating mast cell granule dynamics.