3H Pro Leu Gly NH 2, a melanocyte stimulating hormone release inhibiting factor (MIF), was injected into 5 healthy men. A plot of the time of the disappearance of radioactivity in plasma was characteristic of a multiexponential curve. The half life of the first component was 1.9±0.06 min and of the second component 15.2±1.5 min. The distribution volume was 20% of the body weight. One hour after the injection of labeled MIF, 17.2±0.7% of the dose of radioactivity was found in the urine and after 24 hr 25% had been excreted. Extraction of the urine, followed by chromatography on carboxymethyl cellulose and thin layer electrophoresis, showed that over 70% of the radioactivity was associated with the intact molecule while a smaller amount appeared to be either free proline, Pro Leu OH, or the deaminated form of the tripeptide. It appears that the main pathway for the clearance of MIF from the human body is excretion of the intact molecule.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience