Pituitary and Plasma Lipotropins: Demonstration of the Artifactual Nature of βMSH

Abstract

Evidence has been presented by others that βSMSH immunoreactivity in human plasma is due to β and γ lipotropin rather than βMSH. We have studied this question in normal subjects utilizing a sensitive human /3MSH radioimmunoassay capable of quantifying βMSH in unextracted plasma with a sensitivity of 7.5 pg/ml. Purified human /3 lipotropin cross-reacted 30% on a molar basis with synthetic human βMSH in this assay. ACTH related peptides showed per se in human pituitaries, plasma from metyrapone treated normals, patients with Cushing's disease, Nelson's syndrome, or Addison's disease. βMSH immunoreactivity showed the elution pattern of βlipotropin.