Glucocorticoid secretion

In addition to effects mediated through glucocorticoid secretion (stress-related), a hypothetical mechanism for direct immunotoxicity of organophosphates is the inhibition of esterases and stabilization of the lysosomal membrane of lymphocytes, thus blocking release of lymphokines (Sharma and Reddy 1987). 

Horai, R. et al., Production of mice deficient in genes for interleukin (IL)-la, IL-ip, and IL-1 receptor antagonist shows that IL-lp is crucial in turpentine-induced fever development and glucocorticoid secretion, J. Exp. Med., 187, 1463, 1998. 

Barbazanges, A. et al., Maternal glucocorticoid secretion mediates long-term effects of prenatal stress, J. Neurosci., 16, 3943, 1996. 

Glucocorticoids and mineralocorticoids are uniquely produced by the adrenal cortex, and are collectively termed corticosteroids. Apart from aldosterone, glucocorticoid secretion is regulated by the pituitary hormone, corticotrophin. The principal corticosteroids synthesized in the body are illustrated in Figure 1.6. Glucocorticoids generally exhibit weak mineralocorticoid actions and vice versa. 

The important glucocorticoid secreted in human being is hydrocortisone (10 mg/ day). They are listed in table 8.3.1. 

Mood changes continue to be reported in association with corticotropin (15). Emotional instability or psychotic tendencies can be aggravated, while euphoria, insomnia, and personality changes such as hypomania and depression can be precipitated, sometimes even with psychotic manifestations. Although it seems reasonable to assume that one is dealing here mainly with an effect of the glucocorticoids secreted in response to corticotropin, it should be recalled that segments of the corticotropin molecule themselves have effects on brain function and could conceivably play a role. 

In addition to the angiotensin II effects, aldosterone secretion is regulated by increased plasma potassium levels.75,83 Presumably, elevated plasma potassium serves as a stimulus to increase aldosterone release, thus causing increased potassium excretion and a return to normal plasma levels. Finally, there is evidence that ACTH may also play a role in aldosterone release. Although ACTH is primarily involved in controlling glucocorticoid secretion, this hormone may also stimulate mineralocorticoid release to some extent.75... 

Glucocorticoids alter the DNA transcription process in their target tissues. They adapt the body to stress. Glucocorticoids also promote the rapid provision of glucose and fatty acids for energy and permit the responses of the circulation required in reaction to stressful events. When glucocorticoid secretion is chronically increased, there is suppression of the immune system patients experience poor wound healing and increased susceptibility to infection. 

Q4 Glucocorticoid secretion is controlled by the hypothalamus and anterior pituitary gland. Corticotrophin releasing factor (CRF) is produced in the hypothalamus and travels in the hypophyseal portal blood vessels to the anterior pituitary to release ACTH (adrenocorticotrophic hormone). There is a daily (circadian) rhythm in CRF and ACTH secretion, with a peak in the morning between 7 and 9 a.m. and a low point during the night. 

Addison s disease results from reduction in glucocorticoid secretion, which maybe caused by infection or autoimmune disease. In the latter, proliferation of immunocytes against specific antibodies occurs because of a deficiency of immune suppresser cells in the adrenocortical cells. This causes chronic reduction in the levels of aldosterone and cortisol. Reduced aldosterone secretion decreases renal sodium and water reabsorption, leading to hypovolaemia and... 

Marked leukocytosis has been described, despite the absence of infection, in a patient treated with tetracosactide (SED-12, 980) the effect may well have been due to glucocorticoid secretion rather than to tetracosactide itself. 

Glucocorticoid secretion from the adrenal cortex is stimulated by corticotropin or adrenocorticotropic hormone (ACTH) that is released from the anterior pituitary in response to hypothalamic-mediated release of corticotropinreleasing hormone (CRH). 

Anabolic hormones will be effective if nutrition of the animal is adequate. Inadequate food intake leads to a stress condition in the animal which stimulates glucocorticoid secretion. Glucocorticoid secretion in turn decreases protein synthesis and increases amino acid catabolism [12]. 

---