Chronic exposure to constant light affects morphology and secretion of adrenal zona fasciculata cells in female rats

The effect of chronic exposure to light of adult Wistar rats on growth and function of adrenal zona glomerulosa (ZG) and zona fasciculata (ZF) were examined. The females were exposed to continuous light of 600 lux for 95 days, starting on day 30 of age. The controls were kept under a 12 : 12 h light-dark cycle, at ambient temperature. The rats were sacrificed by decapitation and the left adrenal gland of each animal was dissected out and prepared for morphometric analyses. In animals exposed to chronic lighting, the absolute and relative volume of ZG were insignificantly increased by 5% (p > 0.05) compared to controls. The volume of ZG cells and their nuclei were insignificantly changed by 1% (p > 0.05) in comparison with corresponding controls. The absolute and relative volume of ZF were significantly increased (by 14 and 9%, respectively, p < 0.05), as compared to controls. The volume of ZF cells and their nuclei were significantly increased (by 12 and 9%, respectively; p < 0.05). Serum concentration of corticosterone was also significantly (p < 0.05) increased by 13 % in light-exposed group in comparison with control rats. These findings suggest that continuous exposure of female rats to constant light increased growth and secretory activity of ZF cells.