Gamma-melanotropin response to ovine corticotropin releasing factor in normal humans

Plasma gamma-melanotropin was measured by a gamma 3MSH-specific radioimmunoassay before and after a single bolus intravenous infusion of ovine corticotropin releasing factor (oCRF; 0.1 microgram/kg) in seven normal men. A significant increase of gamma 3MSH was observed 15 minutes post-oCRF infusion, which paralleled a similar increase in plasma cortisol. Gel filtration chromatography revealed that the observed increase was attributable to elevations of 9K and 4K forms of gamma 3MSH immunoreactivity. Affinity chromatography demonstrated that the majority of gamma 3MSH immunoreactivity in human plasma is glycosylated. As the smaller forms of gamma 3MSH are felt to have endocrine activity at the adrenal cortex, these changes may be physiologically relevant.