Localization of β-Endorphin in the Rat Heart and Modulation by Testosterone

AbstractChromatographic analysis and radioimmunoassay were used to identify and quantitate β-endorphin (BE) and β-lipotropin (B-LPH) in the hearts (devoid of major blood vessels and atria) from intact male rats, castrated male rats, and castrated male rats treated with testosterone proprionate (TP). BE and B-LPH in the plasma of these animals were also identified and measured. In comparison to intact animals, castration resulted in a significant elevation in the content of BE in the heart which was reversed by the administration of TP. The content of B-LPH in the heart was not affected by castration or castration in combination with TP. The ratio of BE to B-LPH in the heart of castrated animals was significantly elevated as compared with intact controls. Treatment of castrates with TP returned the ratio of BE to B-LPH to that observed in intact animals. The concentration of BE in the plasma was greater in castrated rats and castrated rats given TP than in intact males, whereas the concentration of B-LPH w...