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Autonomous beta-endorphin secretion from the pituitary neurointermediate lobe: in vivo studies

Autonomous beta-endorphin secretion from the pituitary neurointermediate lobe: in vivo studies

Life Sciences 34(16): 1605-1611

The existence of independent control mechanisms of .beta.-endorphin (.beta.-EP) secretion from the anterior (AP) and intermediate (NIL) pituitary lobes was ascertained. The effect of surgical separation from the hypothalamus of the 2 pituitary lobes on .beta.-EP secretion was evaluated. Two experimental models of surgical hypothalamo-pituitary disconnection were used: rats with ablation of the medial basal hypothalamus (MBH); rats bearing 2 entire ectopic pituitaries or 2 only, transplanted under the kidney capsule. In rats with MBH-ablation plasma .beta.-EP levels were significantly higher than in sham-operated controls. Plasma .beta.-EP levels increased in rats transplanted with entire pituitaries 3 days after surgery and were still elevated after 1 wk. In rats transplanted with AP only, no significant .beta.-EP changes in plasma were evident. In both experimental conditions no significant difference was present in .beta.-LPH [.beta.-lipotropin] plasma levels. Concentrations of .beta.-EP in the ectopic NIL decreased gradually after transplantation. Evidently, the NIL but not the AP is capable, when it is disconnected from the hypothalamus, of secreting autonomously .beta.-EP.

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Accession: 004802997

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PMID: 6325841

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