AJP - Endocrinology and Metabolism, Vol 242, Issue 4 226-E233, Copyright © 1982 by American Physiological Society
Autoregulation of rat pituitary prolactin secretion demonstrated by a new perfusion method
H. A. Zacur, W. E. Mitch, J. E. Tyson, P. T. Ostrow and G. V. Foster
Regulation of prolactin secretion was investigated by perfusing rat
pituitaries in vitro. Two pituitary glands from inbred rats were
transplanted beneath the renal capsule of a third recipient rat. Three
weeks later, the transplanted kidney was removed and perfused in vitro with
a defined cell-free medium. Normal renal function was maintained during
perfusion, and cell morphology of the transplants remained unchanged as
assessed by electron microscopy. Pituitary prolactin content did not change
after 120 min of perfusion despite release of approximately 10 micrograms
of hormone. Thyrotropin-releasing hormone (10 ng/ml) did not stimulate
prolactin release; dopamine (20 ng/ml) rapidly, but transiently inhibited
prolactin release; bromocriptine (20 ng/ml) rapidly and persistently
inhibited prolactin release; haloperidol (100 ng/ml) blocked the inhibition
by dopamine or bromocriptine, but when given alone inhibited prolactin
release. Finally, prolactin release was also inhibited by the presence of
100 and 200 ng/ml, but not 50 ng/ml of NIAMDD RP-1 rat prolactin. It is
concluded that in vitro perfusion of transplanted rat pituitaries provides
a new model for studying the direct effect of agents on the secretion of
prolactin from the pituitary and that rat prolactin and/or its metabolites
directly inhibit pituitary prolactin secretion.
