Ultrastructure of Ampullar Dark Cells in the Absence of Circulating Adrenocorticosteroid Hormones

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Abstract
The morphology of rat ampullar dark cells was studied in the absence of circulating adrenal hormones at two time intervals of 8-14 and 22-28 days. Five morphological parameters of dark cells were quantitatively determined: cell area per baseline length, basolateral membrane surface density, basolateral membrane length per baseline length, volume density of intercellular space and volume density of vacuoles. Significant statistical reduction of basolateral membrane length per baseline length was observed after an absence of circulating adrenal hormones for 8-14 days and 22-28 days compared to sham operated animals that served as control. The basolateral membrane surface density decreased significantly in the animals sacrificed 22-28 days following adrenalectomy compared to sham operated animals. Cell area per baseline length decreased and volume density of vacuoles increased at both time intervals following adrenalectomy; however, these differences were statistically insignificant. The volume density of intercellular space between dark cells was practically constant among the groups. Results of this study are similar to those reported for ion-regulating nephron cells, and support the hypothesis that cells involved in microhomeostasis of vestibular endolymph may at least be partly regulated by adrenal hormones.