Immunoreactive endorphins, lipotropins and corticotropins in a human nonpituitary tumor: evidence for a common precursor.

The immunoreactive (RIA), ACTH, LPH, alpha endorphin (alpha End) and beta End in an extract of a human pancreatic islet cell carcinoma causing the ectopic ACTH syndrome were assayed after gel exclusion chromatography. In addition to "big", "intermediate" and "little" ACTHs, beta lipotropin (beta LPH) and gamma LPH, the eluate fractions contained RIA-alpha End and -beta End. The major RIA-beta End component appeared to be h beta LPH, which has beta End as its carboxy-terminus, but significant concentrations of a component that coeluted with synthetic p beta End were also found. Small amounts of RIA-alpha End were found in two peaks, one that may have represented 1-76 h beta LPH, with alpha End as its carboxy-terminus, and one probably representing alpha End itself. RIA-ACTH, -LPH and -beta End were found in the void volume fractions. Thus, a human nonpituitary tumor that produced ACTH and LPHs also produced endorphins, all perhaps deriving from a common precursor.