ULTRASTRUCTURE OF THE ADRENAL-CORTEX OF HIBERNATING, AROUSING, AND EUTHERMIC DORMOUSE, MUSCARDINUS-AVELLANARIUS

Background: The adrenal gland is a key organ for hibernation (a condit ion characterized by striking reduction of body functions), Very limit ed information is available on the fine structure of the gland during hibernation and on the periodical arousal from hibernation, Methods: D ormice (Muscardinus avellanarius) were maintained in an external anima l house and allowed to hibernate spontaneously (November). Arousal was induced in March by exposure to daylight. Euthermic, active dormice w ere captured in June, The adrenals were taken from four hibernating, t hree arousing, and four euthermic dormice and processed for resin embe dding, The ultrastructure of the adrenal cortex was investigated by tr ansmission electron microscopy. Results: In the zona glomerulosa of hi bernating and arousing dormice, the smooth endoplasmic reticulum was p rominent in comparison with euthermic animals, and mitochondria showed abundant vesicular cristae. The zona fasciculata and zona reticularis did not show consistent differences, apart from a lower cell lipid co ntent in the outer portion of zona fasciculata of arousing dormice. Co nclusions: The zona glomerulosa showed signs of increased activity dur ing hibernation, This finding is supported by previous biochemical dat a demonstrating increased production of renin and aldosterone during s uch extreme physiological conditions, Activation of the zona glomerulo sa in hibernation is probably adaptive to a condition of drastically r educed salt intake. (C) 1997 WiIey-Liss, Inc.