Histological Changes in the Adrenal Cortex of Wistar Rats Following Prolonged Exposure to Noise Pollution: A Model for Urban Lagos

Noise pollution is an increasingly recognised environmental health hazard in Nigerian urban centres, with Lagos amongst the noisiest cities in West Africa. Chronic noise exposure activates the hypothalamo-pituitary-adrenal axis, potentially causing structural changes to the adrenal cortex through persistent glucocorticoid hypersecretion. Despite the widespread human exposure to occupational and environmental noise in Lagos, experimental anatomical evidence quantifying adrenal cortical histological changes in this context is lacking. This study aims to evaluate histological changes in the zona glomerulosa, zona fasciculata, and zona reticularis of the adrenal cortex in Wistar rats subjected to chronic intermittent noise at sound pressure levels representative of Lagos urban traffic. Forty Wistar rats will be exposed to noise at 85 decibels for 8 hours daily over 12 weeks, with controls maintained in ambient laboratory conditions. Adrenal cortical sections stained with haematoxylin and eosin and Sudanophilic fat stains will be examined for hypertrophy, cellular vacuolation, and lipid depletion. Adrenal gland weight and cortical thickness will be morphometrically quantified. Plasma cortisol levels will supplement histological findings. The study expects to demonstrate progressive structural changes in the adrenal cortex attributable to chronic noise stress.

Keywords: adrenal cortex, noise pollution, histomorphometry, stress response, Wistar rats