Metabolism of a peptide of human myelin basic protein in the rabbit.

Material cross-reactive with myelin basic protein (BP) peptide 43-88 has been identified as a major BP-like antigen appearing in human cerebrospinal fluid during acute myelin injury. In an effort to develop a means for detecting this material in the more accessible body fluids of blood and urine, as well as to determine its metabolic fate, the manner in which rabbits handle human BP peptide 43-88 was investigated. Unlabeled peptide was administered intravenously, and its concentration in plasma was monitored by radioimmunoassay. In studies of 10 rabbits, the peptide disappeared from blood in two phases, the first showing a half-life of 6.0 +/- 1.2 minutes and the second a half-life of 51.6 +/- 5.4 minutes. Organ-exclusion experiments indicated a rapid clearance, predominantly by the kidney, for the peptide, with tubular reabsorption and cleavage into smaller peptide fragments a probable catabolic mechanism.