Endocrinology, Vol 96, 1210-1215, Copyright © 1975 by Endocrine Society

ARTICLES

In vitro release of lutenizing hormone from anterior pituitary fragments superfused with constant or pulsatile amounts of luteinizing hormone-releasing factor

RB Osland, RV Gallo and JA Williams

Anterior pituitary fragments from ovariectomized rats were superfused with medium to which lutenising hormone-releasing factor (LH-RF) was added for either prolonged or short intervals. Samples of superfusate were collected at 2-min intervals before and after the onset of LH-RF administration. In control experiments without anterior pituitary fragments, infusions of constant amounts of NIAMDD-Rat LH were made into the superfusion chamber. The superfusate was collected in all experiments and luteinizing hormone (LH) levels measured by radioimmunoassay. LH release was increased 100-200% following superfusion with concentrations of LH-RF ranging from 10-9 to 10-5M. The percent coefficient of variation (%CV) was determined for LH to quantitate fluctuations in hormone release. A nonepisodic pattern of LH release was obtained prior to LH-RF administration and during superfusion with constant levels of LH-RF. There was no significant difference in the %CV in these periods as compared to that obtained during infusion of constant amounts of LH into the superfusion chamber. However stimulation by LH-RF for only 2-5 min caused episodes of LH release lasting 30-40 min. The %CV of superfusate LH during these pulsatile stimulation studies was significantly increased compared to that obtained during superfusion with constant levels of LH-RF. These results suggest that the pituitary is not the site of origin of the mechanism underlying episodic release of LH, but can release LH in a pulsatile manner when driven by pulsatile LH-RF stimulation.