Protein synthesis and transport by the rat choroid plexus and ependyma: an autoradiographic study

Light (LM-ARG) and electron microscope (EM-ARG) autoradiographs were preapred from immature rat choriod plexus and ependyma at 5, 10, 30, and 60 min and 16 h following intraperitoneal administration of [3H]labeled amino acid mixtures. Intracellular protein synthesis and transport were ascertained in lateral and fourth ventricle choroid plexus epithelium by quantitative EN-ARG at the several post-injection intervals. ARG were also prepared from choriod plexuses cultured for one day, pulse labeled for one hour and reincubated for various periods in nonradioactive media. Significant labeling of both attached and free apical protrusions (blebs) was observed in both choroid plexus and ependyma in vivo and in choroid plexus in vitro. This phenomenon was interpreted as a physiologically significant mechanism for protein trasport (apocrine secretion) by epithelia into the cerebrospinal fluid (CSF).