COMPARISON OF THE EFFECTS OF IMMOBILIZATION AND PRESSURE-OVERLOAD INDUCED CARDIAC-HYPERTROPHY ON IMMUNOREACTIVE BETA-ENDORPHIN

Acute physical stress in the form of immobilization resulted in a decr ease 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 plasm a. Hypothalamic IR-BE was not influenced by immobilization. In respons e to chronic cardiovascular (physiological) stress resulting from cons triction of the aorta (aortic banding) and subsequent pressure overloa d, the concentration of IR-BE in the AP was increased as was the conce ntration of IR-BE in the plasma. The concentration of IR-BE in the NIL and the hypothalamus was not affected. These findings suggest that ph ysical stress and cardiovascular stress have the same affect on IR-BE levels in the plasma but differ in their respective effects on IR-BE i n the AP and NIL and do not affect the concentration of IR-BE in the h ypothalamus. The difference in the effects of each form of stress on t he AP and the NIL respectively, may be attributed to either the type o f stress employed (physical versus physiological), the duration of the stress (acute vs chronic), or both.