Dopamine requires ascorbic acid to be the prolactin-release
inhibiting factor (pif).
Shin, Seon H., Fengqin Si, and Gregory M. Ross.
Departments of Physiology and Medicine, Queen's University,
Kingston, Ontario, Canada K7L 3N6
APStracts 4:0126E, 1997.
A high concentration of dopamine (10-6 mol/L) inhibited prolactin
release for less than 60 min during a 2 h perifusion period using
primary cultured pituitary cells. However, when dopamine (10-6 mol/L)
and control medium were alternately perifused, dopamine inhibited
prolactin release for a longer period, indicating that the inability
of dopamine to sustain an inhibitory action is likely caused by
decreased sensitivity of the lactotrophs to dopamine. When 3x10-7
mol/L dopamine was perifused, prolactin release was inhibited for
only 15 min, and the rate of prolactin release was decreased to a
nadir by adding ascorbic acid (10-4 mol/L) 15 min after beginning
dopamine perifusion. Dopamine decreased density of D2-receptors and
ascorbic acid inhibited the receptor down-regulation in GH4ZR7 cells.
These results support our hypothesis that dopamine requires a
supplementary agent to be the prolactin-release inhibiting factor
(PIF) and that the supplementary agent is ascorbic acid.
Received 1997 March 4; accepted in final form 1997 May 21
APS Manuscript Number E097-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 1 July 1997