beta-endorphin and Cardiomegaly

Acute physical stress in the form of immobilization resulted in a decrease in the concentration of immunoreactive beta-endorphin (IR-BE) in the anterior pituitary (AP) and an increase in the concentration of IR-BE in the neurointermediate lobe of the pituitary (NIL) and the plasma. Hypothalamic IR-BE was not influenced by immobilization. In response to chronic cardiovascular (physiological) stress resulting from constriction of the aorta (aortic banding) and subsequent pressure overload, the concentration of IR-BE in the AP was increased as was the concentration of IR-BE in the plasma. The concentration of IR-BE in the NIL and the hypothalamus was not affected. These findings suggest that physical stress and cardiovascular stress have the same affect on IR-BE levels in the plasma but differ in their respective effects on IR-BE in the AP and NIL and do not affect the concentration of IR-BE in the hypothalamus. The difference in the effects of each form of stress on the AP and the NIL respectively, may be attributed to either the type of stress employed (physical versus physiological), the duration of the stress (acute vs chronic), or both.

Topics: Animals; beta-Endorphin; Blood Pressure; Cardiomegaly; Hypothalamus; Male; Pituitary Gland; Rats; Rats, Sprague-Dawley; Restraint, Physical; Stress, Physiological

In the present study, beta-endorphin (BE), beta-lipotropin (B-LPH) and the ratio of beta-endorphin to beta-lipotropin (BE:B-LPH) were determined in rat cardiac tissue in response to physical stress induced by immobilization and cardiovascular stress resulting from hemorrhagic shock and pressure overload-induced cardiac hypertrophy. As compared with controls, BE was increased and B-LPH was decreased in cardiac tissue from animals subjected to immobilization, and there was also a significant rise in the ratio of BE:B-LPH. Cardiac BE remained unchanged following hemorrhage, while B-LPH was diminished, resulting in an increase in the ratio of BE:B-LPH. Similarly, the concentration of BE was unchanged, the concentration of B-LPH was significantly diminished and the ratio of BE:B-LPH was significantly increased in hypertrophied hearts. Thus, immobilization-induced stress, hemorrhagic shock, and cardiac hypertrophy all increased the ratio of BE:B-LPH in the heart. However, it appears that immobilization stress induces an increase in cardiac BE, whereas cardiovascular stress results in a preservation of BE in the heart and a reduction in cardiac B-LPH. The data suggests that physical stress (induced by immobilization) and cardiovascular stress (i.e., hemorrhage, hypertrophy) have differential effects on the synthesis of BE and the post-translational processing of proopiomelanocortin in the heart. Furthermore, the alterations in cardiac tissue BE and possibly B-LPH may play a role in the response of the heart to physical and cardiovascular stress.

Topics: Animals; beta-Endorphin; beta-Lipotropin; Cardiomegaly; Male; Myocardium; Rats; Rats, Sprague-Dawley; Shock, Hemorrhagic; Stress, Psychological