Effect of stress and dexamethasone on immunoreactive beta-endorphin levels in rat hypothalamus and pineal.
In response to mild stress the levels of immunoreactive beta-endorphin in rat anterior pituitary, hypothalamus and pineal fell within 10 minutes from 210 to 129 pmol/lobe, 1.47 to 0.89 pmol/mg protein and 2.53 to 0.41 pmol/gland, respectively. No alterations were found to take place in beta-endorphin levels in posterior pituitary or plasma. Dexamethasone pretreatment given 18 h prior to stress resulted in significantly greater reduction of beta-endorphin levels in hypothalamus and pineal than stress alone--hypothalamic levels fell to 0.73 pmol/mg protein and pineal to 0.07 pmol/gland. Plasma beta-endorphin levels in dexamethasone pretreated stressed rats were significantly lower than in intact rats (42 fmol/ml vs. 98 fmol/ml). The almost complete disappearance of beta-endorphin from the pineal in response to stress and dexamethasone suggests that pineal does not itself synthesize the hormone but only utilizes and/or stores it. Gel filtration analysis of the beta-endorphin immunoreactivity in tissue extracts and plasma showed that anterior pituitary and plasma contain three immunoreactive components, eluting like beta-endorphin, beta-lipotropin and proopiocortin, whereas only beta-endorphin-like material was detected in posterior pituitary, hypothalamus and pineal.
D000818:Animals; D002850:Chromatography, Gel; D003429:Cross Reactions; D003907:Dexamethasone / Q000494:pharmacology*; D004723:Endorphins / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000378:metabolism*; D001615:beta-Endorphin
D004723:Endorphins; D001615:beta-Endorphin; D003907:Dexamethasone