Homogenates of male rat hypothalami were fractionated by means of differential centrigugation, and α-melanocyte-stimulating hormone (α-MSH) in the various fractions was quantified by radioimmunoassay. Of the total quantity of α-MSH in the homogenate, 36% was recovered in the 11,500 g pellet and 31% sedimented between 11,500 and 105,000 g. α-MSH was not detected in the 105,000 g supernatant fluid. When the 900 g supernantant fluid was fractionated on continuous sucrose density gradients at non-equilibrium conditions, 2 populations of particles containing α-MSH were observed. When fractionated at equilibrium conditions, the 2 populations were recovered in a single band. These sedimentation characteristics indicate that the particles that contain α-MSH differ in size but are similar in density. After hypo-osmotic shock, the large particles containing α-MSH were not demonstrable, whereas the small particles appeared to be resistant to such treatment. In their sedimnetation, the particles containing α-MSH were indistinguishable from particles containing thyrotropin releasing hormone (TRH) but were separable from those that contained luteinizing hormone releasing hormone (LHRH). It is suggested that the large particles containing α-MSH are synaptosomes.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Neurochemistry|
|Publication status||Published - 1977|
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience