|
|
||||||||
Biology of Reproduction, Vol 5, 59-66, Copyright © 1971 by Society for the Study of Reproduction
1 Department of Physiology-Anatomy University of California, Berkeley, California 94720 The effects of ergotamine tartrate (ET) on prolactin secretion by rat adenohypophysis
in vitro were investigated to ascertain the site of inhibitory action of the drug on the secretion of this hormone. Prolactin levels in incubation medium were estimated by disc electrophoresis and densitometry. Intraperitoneal injection of 1 mg ET 4 hr or 15 hr prior to incubation of the adenohypophyses of the recipient female rats resulted in significant inhibition
of prolactin release in vitro. The drug was more effective after 4 hr than after 15 hr. Addition
of ET to incubation medium at concentrations ranging from 2.5 to 20 µg/ml resulted in
significant inhibition of prolactin release in a 4-hr incubation experiment. A dose-related
effect was obtained over a narrow range of ET concentrations. Concentrations of the drug
ranging from 0.005 to 5.0 µg/ml significantly inhibited prolactin secretion in two organ
culture experiments of 24-hr duration with male rat adenohypophyses. In the first experiment about 40% inhibition of prolactin secretion was obtained at all concentrations of ET.
In the second organ culture study, all concentrations of the drug inhibited secretion by more
than 95%. Thus, no dose-related effect was obtained in either organ culture experiment.
None of the concentrations of ET significantly affected growth hormone secretion in organ
culture. The solvent of the ET containing tartaric acid had no effect on prolactin secretion
in a 24-hr organ culture experiment. Neither the ET nor its solvent containing tartaric acid
had any effect on the detectability of prolactin in the disc electrophoretic-densitometric
assay system. The results indicate that ergot drugs inhibit prolactin-dependent reproductive
processes by depressing the secretion of the hormone by acting directly on the adenohypophyseal lactotropes.
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |