Glycoprotein metabolism in the hypothalamus of rat: significance of glial cells.

Incorporation of 3H-fucose injected into the CSF was studied in hypothalamus and hypophysis of rats by biochemical and autoradiographic techniques. The concentration of radioactivity was determined as a function of time from 10 minutes to 28 days in the acid soluble and the acid precipitable fraction of homogenates. The incorporated activity was localized by light microscopic autoradiography in several regions of the hypothalamus. The labelled proteins were transported to the pars nervosa at a velocity of 1.1 to 3.3 mm/hr, i.e. in the fast component of the axoplasmic flow. Differences were found between hypothalamic and pars nervosa tissue regarding rates of increase and maximum concentrations of protein-bound radioactivity. Values for both parameters were about 6 times higher in hypothalamus than in pars nervosa. On the basis of the autoradiographic observations it is concluded that this difference may be due to a considerably higher synthesis rate of glycoproteins in glial cells than in neurons.