Bovine neurophysin II has prolactin-releasing activity in the estradiol-primed male rat.
In the course of the search for the prolactin-releasing factor (PRF), we noticed that the posterior pituitary contained strong PRF activity and subsequently traced this activity to that of bovine neurophysin-II (NP-II). NP-II prepared in our lab was judged to be a homogeneous preparation according to Sephadex G-75 gel filtration, DEAE ion exchange chromatography and polyacrylamide gel electrophoresis. While neurophysin-I (NP-I) injections of 100 micrograms/kg and 1,000 micrograms/kg elevated plasma prolactin in estradiol-primed male rats to 30% and 50% over the control value, respectively, NP-II doses of 100, 1,000 micrograms/kg increased plasma prolactin concentration in estradiol-primed male rats to 130% and 170% over the control value, respectively. The lowest dose of NP-II needed to increase plasma prolactin concentration was 10 micrograms/kg. Since neurophysin does not stimulate prolactin release from the ectopic pituitary under the kidney capsule nor from lactotrophs in a primary monolayer culture system, neurophysin is believed to act indirectly on the pituitary, presumably through a neurotransmitter and/or hypothalamic releasing (or inhibiting) factor. We propose that NP-II may be one element in the complex chain of the prolactin-releasing mechanism.
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004958:Estradiol / Q000494:pharmacology*; D007016:Hypophysectomy; D008297:Male; D009481:Neurophysins / Q000302:isolation & purification / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D010904:Pituitary Gland, Posterior / Q000032:analysis; D011388:Prolactin / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains
D009481:Neurophysins; D004958:Estradiol; D011388:Prolactin