Rapid and specific radioimmunoassays for beta-endorphin and beta-lipotropin in affinity-purified human plasma

Using rapid and reusable affinity columns, we established a method to measure beta-endorphin (beta END) and beta-lipotropin (beta LPH) separately in human plasma. One column contained antibodies against the N-terminal portion of beta LPH, and the other contained antibodies against beta END. The first column separated beta LPH from beta END and concentrated beta LPH as well, and the second separated beta LPH from concentrated beta END. Mean plasma levels (at 0830-0930 h) of beta END and beta LPH 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 beta END and beta LPH 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 less than 0.001), higher in patients with chronic bone pain (P less than 0.001), and variable in patients with the ectopic ACTH syndrome. These data indicate that beta END and beta LPH can be measured separately in plasma by simple and reproducible procedures.