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Ultrastructural organization of chromaffin cells of rat adrenal glands was studied in different stress models (48 h of running in the wheel, 48 h of immobilization, and sleep deprivation during 7 days). It was shown by ultrastructural morphometry that chromaffin cells experienced fine structural modifications (a decrease in the number of adrenaline- and noradrenaline-containing granules, swelling of mitochondria and endoplasmic reticulum). The degree of such modifications depended on a stress situation, being more pronounced during physical stress.

The ultrastructural organization of secretory granules, containing adrenaline (A) or noradrenaline (NA) was studied in chromaffin cells of the rat adrenal gland after 3-, 24- and 48-hour immobilization stress. Using cytochemical electron microscopic Tranzer's method and the method of morphometry, the number of normal dense cores, "empty" and "semiempty" vesicles was calculated. It was shown that the total content of vesicles and the ratio of investigated types of both adrenaline- and noradrenaline-accumulating granules were markedly changed during stress. The degree of such stress-induced reorganization depended on the stage of stress reaction and involved first A-cells and then NA-cells.

At least three varieties of EC-cells differing in their density, form and fine structure can be revealed at the ultrastructural study of EC- and ECL-cells of the intestinal tract. Different forms of the incretory granules of the ECL-cells and heterogenous ultrastructural organization of their dense contents in man and animals make is possible not only to distinguish several forms of these cellular elements, but to speak of their specific peculiarities. It is not impossible that the ultrastructural peculiarities revealed in the incretory granules of the endocrine cells explain differences in the nature of histologically active substance which they produce.