[Morphological studies of rat adrenal glands after space flight on "Kosmos-1667"].

Histological and histomorphometric examinations of rat adrenals after a 7-day flight revealed the following changes: blood congestion in the cortex and medulla, progressive delipoidization of the cortex, slight enlargement of the nuclear volume of glomerular and fascicular zones, vacuolization of the cytoplasm of medulla cells, reduction of the area of noradrenocyte islets and cell nuclei of the medulla; the adrenal weight remained however unchanged. It is concluded that an early period of adaptation to microgravity was accompanied by a weak stress-reaction. Upon return to Earth the rats developed an acute gravitational stress. From the morphological point of view the stress manifested as: increased volume of nuclei in fascicular cells, decreased content of lipids in them, and greater vacuolization of the cytoplasm of medulla cells. The lack of medulla hypertrophy, reduction of the area of noradrenocyte islets and nuclei of medulla cells suggest that 7-day exposure to microgravity did not exert of stimulating effect on the sympathetic system of rats.