Evidence for prolactin feedback actions on hypothalamic oxytocin, vasoactive intestinal peptide and dopamine secretion.
Ovariectomized rats, when transplanted with 4 anterior pituitaries (APs) to the kidney capsule for 2-3 weeks, had elevated plasma prolactin (PRL) levels (3.8-fold) and showed decreased in situ AP weights (0.62-fold) and PRL concentrations (0.63-fold). The concentrations of dopamine (DA) and oxytocin (OT) in pituitary portal plasma of hyperprolactinemic rats were increased 1.7- and 1.9-fold, respectively. However, the levels of vasoactive intestinal peptide (VIP) in pituitary portal plasma of these rats were decreased 0.31-fold. The secretion of DA, dihydroxyphenylalanine (DOPA) and OT from fetal hypothalamic cells in primary culture was increased, whereas VIP secretion from these cells was reduced in a dose-dependent fashion following PRL treatment. These data are the first in vivo and in vitro demonstration of a stimulatory action of PRL on OT release and an inhibitory action of PRL on VIP release. Furthermore, these data suggest that a subtle imbalance between the secretion of the PRL-inhibiting factor (DA) and the PRL-releasing factors (VIP and OT) during elevated systemic levels of PRL is responsible for decreased lactotrophic function.
Sarkar
D K
DK
Department of Reproductive Medicine, University of California, San Diego, La Jolla.
D000818:Animals; D002478:Cells, Cultured; D004295:Dihydroxyphenylalanine / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005246:Feedback; D005260:Female; D005333:Fetus / Q000378:metabolism; D007031:Hypothalamus / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D007668:Kidney; D010121:Oxytocin / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000637:transplantation; D011388:Prolactin / Q000502:physiology*; D051381:Rats; D011920:Rats, Inbred WF; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*
D014660:Vasoactive Intestinal Peptide; D010121:Oxytocin; D004295:Dihydroxyphenylalanine; D011388:Prolactin; D004298:Dopamine