The in situ imaging of biomolecules and hormones by mass spectrometry imaging allows a more detailed and novel view of adrenal cortical zonation and its function in comparison with classical histological definition. The adrenal glands are two small organs, one located on the top of each kidney. They are part of the endocrine system, a collection of glands that secrete hormones directly into the circulatory system. The adrenal gland is composed of the outer cortex and the inner medulla as main parts. The adrenal cortex is the largest part of an adrenal gland. The cortex itself is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. The other part is the adrenal medulla which is located inside the adrenal cortex in the center of an adrenal gland. It produces “stress hormones,” including adrenaline and noradrenaline. The adrenal cortex and adrenal medulla are enveloped in an adipose capsule that forms a protective layer around an adrenal gland.
Using MSI, the in situ distribution of endogenous metabolites such as catecholamines, sterol and steroid metabolites, nucleotide derivatives, intermediates of glycolysis and tricarboxylic acid cycle, lipids and fatty acids can be visualized and subjected to pathway analyses.
The hormones produced by the adrenal glands help to regulate metabolism, immune system, blood pressure, response to stress and other essential functions. Disorders of the adrenal gland can involve the secretion of too little or too much hormone. A number of endocrine diseases involve dysfunctions of the adrenal gland:
- Cushing syndrome (oversecretion of glucocorticoids)
- Hyperaldosteronism (oversecretion of aldosterone)
- Pheochromocytoma (oversecretion of epinephrine and norepinephrine)
- Virilization (oversecretion of androgens)
Read more about tissue metabolomics reveals a refined functional structure beyond classical histological anatomy.