Rapid and Specific Radioimmunoassays for β-Endorphin and β-Lipotropin in Affinity-Purified Human Plasma*

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Abstract
Using rapid and reusable affinity columns, we established a method to measure (β-endorphin (βEND) and β-lipotropin (βLPH) separately in human plasma. One column contained antibodies against the N-terminal portion of βLPH, and the other contained antibodies against jSEND. The first column separated βLPH from βEND and concentrated βLPH as well, and the second separated βLPH from concentrated βEND. Mean plasma levels (at 0830-0930 h) ofβEND and βLPH in 10 normal subjects were 1.1 ± 0.1 (±SE) and 4.1 ± 0.4 fmol/ml, respectively; both were markedly elevated in patients with ACTH/LPH hypersecretory states. The molar ratios of plasma levels of βEND and βLPH were fairly constant in normal subjects (0.28 ± 0.01), unchanged in patients with Cushing's disease and Cushing's disease after adrenalectomy, lower in patients with Addison's disease (P < 0.001), higher in patients with chronic bone pain (P < 0.001), and variable in patients with the ectopic ACTH syndrome. These data indicate that βEND and βLPH can be measured separately in plasma by simple and reproducible procedures.