82. Pharmacological effect of glucocorticoids, and the physiology of the stress

Question 1

Pharmacological effect of glucocorticoids

Answer 1

Glucocorticoids are utilized in veterinary practice mainly because of their excessive anti- inflammatory effect.

It is important to know that glucocorticoids administered in (high) pharmacological doses may exert certain effects, that are different from physiological ones.

Question 2

high level

Answer 2

The effects of continuous high level of glucocorticoids (stress or exogenous administration):
– On mesenchymal cells
– anti-inflammatory
– Antiallergic effect’

Question 3

Antiallergenic effects:

Answer 3

Antiallergenic effects:
– glucocorticoids significantly inhibit histamine release
– they do not have a direct influence on antigen - antibody reaction

Question 4

Stress

Answer 4

Organisms are exposed to constant environmental effects. For the maintenance of the internal environment the organism avoids stimuli that would shift the equilibrium.
If the stimulus is very strong or it may disturb the internal equilibrium state (“noxious stimulus), defence mechanisms are put into force by the organism.

• Specific response is a possibility of defence, like antibody response to a virus infection.
• During functioning of the immune system, specific antibodies are produced against the given virus, and the organism can recover from illness in favorable conditions.
• In case of noxious stimuli, when specific response is not available, the organism’s reaction is nonspecific i.e., the same to every stimulus. This reaction is called stress-reaction. This form of adaptation is called “general adaptation syndrome (GAS)” according to the works of János Selye.
• Stress is elicited by stressors. Every stimulus has to be considered as a stressor, if it leads to the development of GAS

Question 5

Stressors

Answer 5

Physical stimuli:

• mechanical stimuli
• surgical intervention
• limitation of motion
• temperature
• effects of electricity,
• weather

Specific pathogens:
-virus, bacterium, parasite

Related to feeding:
deficiencies: vitamins, micro elements, intoxications

Emotional stimuli:
psychic stress, pain, lack of stimuli

Question 6

Phases of stress

Answer 6

There are four phases of stress response.

1.Initial stage: During stress, release of ACTH starts immediately. The development of stress is often accompanied by Cannon’s alarm reaction. The effect of catecholamines declines within a few minutes, but ACTH level remains high.

2.Stage of resistance: The adrenal cortex produces a high amount of glucocorticoids. As a result unnecessary functions are rapidly reduced to the minimum. Functioning of the immune system becomes inhibited, storing processes are terminated.
Because of the excessive glyconeogenesis, hyperglycemia is persisting, but it does not elicit insulin secretion. The energy needs of the body are covered by burning of fat. Protein stores, muscles are decomposed and amino acids released here are utilized for the synthesis of carbohydrates.
Within these conditions, the organism is able to resist the effects of the stressor for a longer period. If the noxious effect persists, there are two possibilities:

3. Stage of exhaustion: The energy reserves of the organism expire, stage of collapse starts and the animal dies.
4. Stage of adaptive disorders: Adaptive disorders, such as arthritis, chronic hypertension, ulcer and hepatic failure, etc.

Question 7

Inhibition of the proliferation of mesenchymal cells:

Answer 7

– Fibroblast and collagen formation is inhibited.
– Normal granulation and total healing of the wound are inhibited.
– Osteolysis is remarkable: osseous matrix is degraded, calcium is mobilized and excreted and, in the end, osteoporosis develops.

Question 8

Anti-inflammatory (antiphlogistic) effect

Answer 8

The most important effects of glucocorticoid treatment in veterinary practice, which are due to the phospholipase A2 blocking effect of glucocorticoids are the following:

-the decrease of inflammatory color, dolor and tumor:
inflammatory processes go along with changes of color (color), pain (dolor) and swelling (tumor).

-Glucocorticoids drastically moderate all three symptoms.
they decrease basophil degranulation (significantly decrease allergic reactions).

• masking effect: since corticoid treatment only decreases inflammatory symptoms, it is not meant to be a causal treatment
• The inflammation inducing bacteria can proliferate in the tissue and the treatment with them can hide the real etiology of the disease.