Role of Adrenal Glands in Renal Physiology

The role of adrenal glands in the control of functioning of kidneys is very well established in terms of renal physiology. Every organ of our body has an embryonal origin and relationship with other organs. This relationship helps us to establish the physiology of systems associated with each other. There exists a pair of adrenal glands in our body and their position is suprarenal. Each adrenal gland has a cortex and medulla. There exists three layers of specialized cells in the adrenal cortex and these are: (1) Zona glomerulosa, (2) Zona fasciculata and (3) Zona reticularis. The medullae of adrenal glands belong to chromaffin system. The pituitary adrenocorticotrophic hormone (ACTH) controls the activity of adrenal glands in the production of cortisol (hydrocortisone). The inner medullary portion of the adrenal glands produces adrenaline (epinephrine) and noradrenaline (norepinephrine). The adrenal glands function under the control of sympathetic nervous system. The production of adrenal hormones increases in the conditions of emotions like anger or fear and states of asphyxia (lack of oxygen) and starvation and in turn raises the blood pressure in order to overcome the shock. The adrenaline epinephrine) influences the flow of urine and helps in the water balance by kidneys. Noradrenaline norepinephrine) is known to stimulate the muscle fibres in the walls of blood vessels, causing them to contract and thus raising the blood pressure. Adrenaline (epinephrine) also accelerates the carbohydrate metabolism by increasing the output of glucose from the liver.

The cortical layers of adrenal glands produce three types of steroids: (1) Mineralocorticoids are produced by the zona glomerulosa layer of the adrenal cortex and are associated with renal control of water and electrolytes. The mineralocorticoid naturally produced by the adrenal glands is aldosterone which controls the reabsorption of salts by the renal tubules. When there is deficiency of this hormone, too much water and sodium are lost from the body in the urine and too little potassium is excreted and this may lead to toxic levels of potassium in the blood. This results in polyuria, the passage of an excessive quantity of urine. The first of the adrenal steroids isolated or synthesized was the mineralocorticoid called desoxycorticosterone (DOC), which is used in the treatment of shock and polyuria, (2) Glucocorticoids are produced by the middle layer or zona fasciculata of the adrenal cortex and are associated with the metabolism of carbohydrates, fats and proteins. Glucocorticoids promote the conversion of proteins into glucose and storage of glucose as glycogen in the liver. Mineralocorticoids and glucocorticoids complement the action of each other and (3) Androsterone or androgens (sex hormones) are produced by the innermost layer or zona reticularis of the adrenal cortex. Androgens possess 19 carbon atoms in their chemical structure, with one oxygen atom attached to the 17^th carbon atom and are also known as 17-ketosteroids and could normally be detected in the urine. Corticoids are chemically similar to cholesterol, sex hormones or corticosteroids. Our kidneys regulate the volume and composition of our body fluids in terms of water and electrolytes' balance through filtration, secretion, reabsorption and excretion. It is well established that kidneys function under the intelligent control of hormones, without which it would not be possible for the kidneys to maintain a state of homoeostasis in the body.