Regulation function of the adrenal cortex
Endocrinology / / August 12, 2017
Diseases of the adrenal glands and the adrenal cortex
Peripheral nerves that innervate the adrenal glands, in particular the splanchnic nerves, have an impact on the blood supply to the adrenal glands to regulate the speed of blood flow in them.However, they do not have direct impact on regulatory processes of synthesis of adrenal hormones and the release of their blood.
regulation of production and secretion of corticosteroids is performed by humoral.
In 1930, Smith has shown that the removal of the pituitary gland leads to adrenal atrophy;atrophy does not occur if the seat next to the animal tissue of the pituitary.Subsequently it was shown that a major stimulator of cortisol production of corticosterone and 17-keto steroids is pituitary adrenocorticotrophic hormone - ACTH.Regulation of mineral-corticoid production is mainly carried out by other mechanisms, but also ACTH to a certain extent affect the release of aldosterone.
ACTH obtained in purified form simultaneously by two groups of researche
Later it was found that the ACTH is a polypeptide consisting of 39 amino acids.In 1956-1961 gg.They were synthesized polypeptides of 19, 23 and 24 amino acids, possessing properties ACTH.The biological activity of most synthetic polypeptides of less than ACTH activity extracted from pituitary glands.However, synthetic ACTH obtained Kappeler and Schwzer, is not inferior to its activity to the natural hormone.
ACTH stimulates the growth of the adrenal glands, and the synthesis and secretion of adrenal hormones.In the process of biosynthesis of corticosteroids ACTH stimulating effect occurs mainly at the stage of conversion of cholesterol to progesterone.Great importance is attached ACTH ability to stimulate enzyme systems that ensure disintegration of carbohydrates through the pentose cycle, increase the penetration of glucose into the cells of the adrenal cortex.When administered
ACTH reduced cholesterol content, glycogen and ascorbic acid in the adrenal glands, increased protein synthesis in them.Cells beam and reticular zones of the adrenal cortex under the influence of ACTH giperplaziruyutsya and hypertrophy.Changes in the glomerular zone absent or weakly expressed.ACTH causes an increase in oxygen consumption of adrenal tissue, increasing oxidative phosphorylation.
addition to the action on the adrenal glands, ACTH has also ekstraadrenalovym action - lipolytic, ketogenic and sugar-reducing effect, as well as the ability to stimulate melanophores.The ability to stimulate ACTH melanophore cells, non-doped melanoforotropnogo hormone, confirmed by the fact that a small melanoforotropnoy activity have not only ACTH preparations derived from pituitary glands, but also synthetic ACTH.
ACTH circulates in the blood for 3-5 minutes, quickly destroy blood and tissue enzymes and seating in the adrenal glands and kidneys.From the short duration of stay in the blood ACTH it may be connected with the fact that prolonged intravenous drip maximum ACTH stimulation of the adrenal cortex may be achieved with much smaller dosages than with intramuscular formulation.
Regulation ACTH production.In 1945, it has been suggested that stimulant production of ACTH by the anterior pituitary is the adrenaline produced by the adrenal medulla.
has now been found that a large (beyond physiological) doses of epinephrine can stimulate the production of ACTH.
in 1943-1950.it was proved the existence of the reciprocal relationship between cortisol levels in the blood and the secretion of ACTH: a decrease in cortisol levels lead to elevated ACTH production, increasing the concentration of cortisol - to inhibition of ACTH secretion.
In 1952, de Groot and Harris have shown that damage or irritation to the various centers of the hypothalamus results in an increase or inhibition of ACTH production.
stimulating effect on the hypothalamic ACTH production is carried out by humoral.Factor that stimulates ACTH production (CRF - corticotrop in-real ising-factor) enters the anterior pituitary through the portal system.
The data on the participation of the various parts of the central nervous system (almond-shaped nucleus, the hippocampus, the median reticular formation of the brain, some sections of the cerebral cortex) in the regulation of ACTH production.
role of the higher parts of the central nervous system in the regulation of ACTH production is shown by experiments in which conditioned reflex was observed increase in adrenocortical function.
Thus, the regulation of ACTH production can now be represented as follows: the anterior lobe of the pituitary gland has a certain degree of spontaneous activity of adrenocorticotropic.If the damage of the median eminence, or in violation of the vascular pituitary due to hypothalamic-pituitary continues to produce a certain amount of ACTH, sufficient to maintain the "basement" of the adrenal activity.However, in these conditions, the adrenals do not react increasing function in response to conventional stimulators.The whole body, while keeping in touch with an intact pituitary hypothalamus, the main regulator of ACTH production is the hypothalamus, carries out its action by humoral.The various effects hypothalamus summarized as nerve - coming from the upstream and downstream parts of the nervous system, humoral and - primarily cortisol levels.Thus, the hypothalamus is like a final common pathway through which the impact of the various departments of the regulatory systems of the body in the production of ACTH.
production of ACTH by the pituitary gland and the production of corticosteroids by the adrenal cortex in physiological conditions are different at different times of the day.Spontaneous activity rhythm of pituitary - adrenal cortex is innate.Shortly after midnight, a 17-level gidroksikortiko steroids in the blood and excretion of urine begins to rise, peaking at 6 am I;then corticosteroid production begins to decline.At the same time between midnight and 6 am by the adrenal glands is allocated 70% of the daily amount of 17 gidroksikortikosteroidov, and for the rest of the day - 30%.The difference between the maximum and minimum level 17 gidroksikortikosteroidov content in the blood can reach 100%.The cyclic nature of activity of the adrenal cortex does not depend on food intake, nor on the nature of the work or the conditions of life.
Regulation of aldosterone production.There is now enough reliable information on the impact on production of aldosterone changes in the volume of intravascular fluid and ion balance - in plasma sodium and potassium ions.
Reducing the amount of circulating blood due to bleeding, dehydration or moving fluid from the vascular tissue and serous cavities (e.g., liver cirrhosis, nephrosis, heart failure) leads to a significant increase in aldosterone production - 10-40 times.Increased blood volume has an inhibitory effect on the production of aldosterone.The main baroreceptors, which manifests itself through the influence of the circulating blood volume in the production of aldosterone, are located in the area of the carotid sinus in the right ventricular wall.
Equally important in the regulation of aldosterone production than baroreceptors pulses are pulses chemoreceptors located in the cardiovascular system.Increasing the concentration of potassium ions leads to an increase in aldosterone production.Load sodium has an inhibitory effect on the production of aldosterone, and stimulates the production of sodium lack of aldosterone, provided a sufficient content of potassium in the diet.Of particular importance is the ratio of sodium and potassium in the plasma and the reduction ratio of sodium / potassium leads to an increase in aldosterone secretion.
The question of on what paths to the adrenal glands come impulses that stimulate the production of aldosterone, are not updated.There are experimental data suggest that stimulation of aldosterone carried out by humoral.In experiments with cross circulation in dogs compression of the inferior vena cava, or bleeding from the donor dog caused an increase in aldosterone production by the adrenal glands of the recipient dog.
ACTH has a relatively small impact on the production of aldosterone.Glomerular zone adrenal aldosterone is produced in which, after hypophysectomy varies little, as opposed to the beam and a mesh areas exposed with atrophy.However hypophysectomy leads to a decrease in aldosterone production (20-40%) and ACTH administration causes an increase in aldosterone production, according to some, is quite significant.
known stimulating effect on the production of aldosterone angiotensin II (-. A substance having a direct relationship to hypertensive influence renal angiotensinogen produced by the liver under the influence of renin goes to angiotensin I, and then (in plasma) to angiotensin II, which influences on smooth musclesvessels and increases the production of aldosterone. The value of juxtaglomerular apparatus of the kidneys that can produce renin, aldosterone production in the regulation can be considered proven.
in 1959 Farrel isolated from bovine epiphyseal substance called adrenoglomerulotropinom, which has a stimulating effect on the secretion of aldosterone. in the future, it has been decipheredchemical structure adrenoglomerulotropina, and it has been synthesized.
There is evidence of the great importance in the regulation of aldosterone nerve structures adjacent to the epiphysis, in particular the central gray matter in the posterior commissure. Perhaps pineal gland and the adjacent nerve structures are able to exert on the secretion of aldosteronenot only stimulating and the inhibiting effect.In 1960, Farrel the chromatographic separation of the epiphysis extracts obtained fraction that reduces the production of aldosterone in intact and decerebrate dogs.
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At the same time found that the pineal gland removal and surrounding nerve structures, transection of the midbrain and even decapitation dogs do not block the adrenal gland's ability to produce increased amounts of aldosterone ifthe impact of incentives, such as bleeding.
There is evidence that the stimulating effect on the production of aldosterone has a pituitary growth hormone.
are marked daily fluctuations in urinary aldosterone.Usually, in the daytime secretion of the hormone is higher than at night.However, unlike the circadian rhythm of cortisol excretion, are inherent and not dependent on living conditions, fluctuations in aldosterone release may be related to the activity and position of the person.The horizontal allocation of aldosterone decreases, and clock stays in the horizontal position normal circadian rhythm disappeared.