Stress is an organic answer to aversive stimulus or unknown situations to provide the adaptation of host to the new condition. The stressor can be a physical, chemical, emotional and social agent. Different stressors are present in human daily life and can be involved in degenerative diseases and lead to a fast aging process disturbing the body physiology. The main mediators of the stress reaction are the catecholamines (norepinephrine and epinephrine) released by the sympathetic nervous system and by the adrenal medulla, and the glucocorticoids released by the adrenal cortex. The catecholamines and glucocorticoids act in the cells and tissues inducing adaptive changes in order to protect the organism and allow its survival. This response to stressors can be modified by the host and stressor characteristics. Among the host ones, age, gender, and in females, the reproductive cycle are relevant. The variations in the levels of sexual steroids estradiol and progesterone, related to the reproductive cycle, modulate the secretion of CRH, ACTH and glucocorticoids during the stress reaction and are involved in the different responses between men and women. Many studies have shown that the exposure to stressors may induce alterations in the sensitivity to catecholamines in the heart, which are related to adaptive processes. These alterations include changes in the activity of the metabolizing system of catecholamines, in the affinity or number of adrenoceptors, in the coupling between the receptor and G protein, and in enzymes mediating intracellular processes after the receptor activation. The study of these alterations may be helpful to the understanding of the cardiac effects of the water activities and swimming in humans.
Stress; Catecholamines; Reproductive cycle; Heart
