Altered secretory activity in rat adrenal chromaffin cells after experimentally induced bronchial asthma and dexamethasone treatment: ultrastructural and biochemical study

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Abstract

Introduction

It is generally accepted that chromaffin cells release their contents by both exocytosis and piecemeal degranulation (PMD). Bronchial asthma and dexamethasone treatment might alter this secretory activity.

Objective

This study was designed to shed light on secretory activity in the normal adult rat chromaffin cells, in rats subjected to bronchial asthma and after treatment with dexamethasone.

Materials and methods

Rats were divided into three equal groups at random: group A (control), group B (asthmatic rats), and group C (dexamethasone-treated asthmatic rats). In rats of group B, the chronic asthma model was established by an intraperitoneal injection and challenge with ovalbumin. In group C, the rats were pretreated with dexamethasone before each challenge. Serum epinephrine and norepinephrine levels were measured by enzyme-linked immunosorbent assay. Bronchoalveolar lavage fluid was examined for the total leukocytic count and paraffin sections from the lung were stained with H&E. Specimens of the adrenal medulla were examined by transmission electron microscope and were morphometrically analyzed.

Results

Significant decreases in serum epinephrine and norepinephrine levels were recorded in asthmatic rats and corrected after dexamethasone treatment. The total numbers of adrenaline and noradrenaline granules were significantly lower in asthmatic rats. Features of PMD manifested as tail-like projections, altered granules with eroded contents, partially empty granules, large completely empty containers, and small cytoplasmic vesicles were observed in control rats and were augmented in rats subjected to chronic asthma.

Conclusions

Augmented features of PMD and biochemical changes in the conditions of chronic asthma could be corrected by dexamethasone treatment.

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