Ultrastructural studies on characteristics of exocytosis of chromaffin cells in adrenal medulla of restrained rats

Transmission electron microscopy was used to study the characteristics of exocytosis of chromaffin cells in adrenal medulla during emergency reaction of restrained rats. It was found that three types of exocytosis existed: single granule exocytosis, multigranule successive exocytosis and exocytosis through a temporary fusion pore. Two kinds of granule were estimated by using stereological morphometry. The results showed: the number of dense core granules was more than that of shallow core granules ( P 0 01). When the rats were restrained for 8h, we found that only the dense core granules decreased. When the restrained time was extended to 24h, both two kinds of granule decreased. It is suggested that these two kinds of granules may be the same secretory granules of chromaffin cells, which are in the different developmental stages.