Subcellular distribution of hypothalamic prolactin-like immunoreactivity.
Prompted by interest in immunohistochemical reports of prolactin-like immunoreactivity (PLI) in the rat hypothalamus, we investigated and have reported that an immunoreactive and bioactive prolactin-like material can be extracted from the rat hypothalamus. In the present communication the subcellular distribution of this protein is reported. Using a sensitive and specific radioimmunoassay for rat prolactin and a standardized procedure for subcellular fractionation of neuronal tissue, we have found that 90% of hypothalamic PLI is particulate-bound with only 10% remaining in the S4 or cytosolic fraction. Almost 80% of the particulate-bound PLI is found in the P2 fraction containing myelin, synaptosomes and mitochondria. When P2 is further fractioned on a discontinuous sucrose density gradient, approximately 66% of the P2-associated PLI was found in subfractions rich in synaptosomes and poor in myelin and mitochondria. Such findings support the probability that hypothalamic PLI functions trans-synaptically as a neuromodulator in the brain.
D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D002458:Cell Fractionation; D003600:Cytosol / Q000032:analysis; D007031:Hypothalamus / Q000032:analysis*; D008297:Male; D011388:Prolactin / Q000032:analysis*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000032:analysis; D013574:Synaptosomes / Q000032:analysis
D011388:Prolactin; D000110:Acetylcholinesterase