OESTRADIOL-17β INCREASES PITUITARY RESPONSIVENESS BY A MECHANISM THAT INVOLVES THE RELEASE AND THE PRIMING EFFECT OF LUTEINIZING HORMONE RELEASING FACTOR

1981 ◽  
Vol 88 (2) ◽  
pp. 301-308 ◽  
Author(s):  
ALISON SPEIGHT ◽  
RACHEL POPKIN ◽  
A. G. WATTS ◽  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Priming Effect ◽  
Anterior Pituitary Gland ◽  
Silicone Elastomer ◽  
Pituitary Stalk ◽  
Adult Rats ◽  
Peripheral Plasma

We have investigated the mechanism by which oestradiol-17β augments pituitary responsiveness to luteinizing hormone releasing factor (LH-RF). Adult rats were ovariectomized on the morning of dioestrus and implanted with either an empty silicone elastomer capsule or a capsule containing oestradiol-17β. Twelve hours later the LH response, tested by injecting 50 ng LH-RF/100 g i.v., was significantly greater in animals implanted with an oestradiol capsule compared with that in animals implanted with an empty capsule. The effect of oestradiol was blocked by sodium pentobarbitone administered 4 h before the test, and this block was overcome by infusing LH-RF during the 4 h period at doses which by themselves were not sufficient to evoke a large release of LH. We also measured LH-RF in pituitary stalk blood collected under Althesin anaesthesia between 4–6 and 12–13 h after ovariectomy and capsule implantation. The concentration of LH-RF in stalk plasma fell between these two collection periods in animals implanted with empty but not with oestradiol-filled capsules. The concentrations of LH-RF in stalk plasma, although relatively low, were significantly higher in animals bearing an oestradiol-containing capsule than the concentrations in peripheral plasma from similarly treated animals, and, by comparison with the LH-RF concentrations in peripheral plasma from animals infused with LH-RF, were sufficiently high to increase significantly the responsiveness of the pituitary gland. These data show that as well as acting directly on the pituitary gonadotrophs, oestradiol-17β increases the responsiveness of the anterior pituitary gland by a mechanism that involves the release and the priming effect of LH-RF.

ONTOGENY OF THE SENSITIZING EFFECT OF OESTRADIOL AND LUTEINIZING HORMONE RELEASING HORMONE ON THE ANTERIOR PITUITARY GLAND OF THE FEMALE RAT

1981 ◽  
Vol 91 (2) ◽  
pp. 347-351 ◽  
Author(s):  
R. MEIDAN ◽  
G. FINK ◽  
Y. KOCH
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Priming Effect ◽  
Anterior Pituitary Gland ◽  
Female Rats ◽  
Facilitatory Effect ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh

The ontogeny of the facilitatory effect of oestradiol and luteinizing hormone releasing hormone (LH-RH) on the responsiveness of the anterior pituitary gland to LH-RH has been studied in vitro using pituitary glands from female rats aged 15, 17, 20, 31, 35 and 38 days. The facilitatory effect of oestradiol was already well established by day 15, while the facilitatory effect of LH-RH (priming effect) developed only after day 17. Although it increased the overall response of the gland to LH-RH, oestradiol did not selectively enhance the priming effect of LH-RH. Both the effect of oestradiol and LH-RH reached a peak on day 25, 7 days before vaginal opening in this colony, and, as assessed by measuring pituitary LH contents, were not dependent upon the synthesis of LH. These data show that different mechanisms may be involved in the facilitation of pituitary responsiveness by oestradiol and LH-RH, but that both mechanisms appear to depend more upon an increase in the sensitivity of the receptor/release apparatus rather than in the gonadotrophin content of the gonadotrophs.

A PRIMING EFFECT OF LUTEINIZING HORMONE RELEASING FACTOR ON THE ANTERIOR PITUITARY GLAND IN THE FEMALE RAT

1974 ◽  
Vol 62 (3) ◽  
pp. 573-588 ◽  
Author(s):  
M. S. AIYER ◽  
SHARON A. CHIAPPA ◽  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Priming Effect ◽  
Plasma Concentrations ◽  
External Jugular Vein ◽  
Anterior Pituitary Gland ◽  
Female Rat ◽  
Oestradiol Benzoate ◽  
Plasma Oestradiol

SUMMARY The possibility that luteinizing hormone releasing factor (LH-RF) not only stimulates the secretion of luteinizing hormone (LH) but also has the ability to prime the anterior pituitary gland so that further exposure to LH-RF enhances the responsiveness of the gonadotrophs has been investigated. The effect of two successive i.v. injections of the same dose of LH-RF (50 ng/100 g body weight) on the concentration of LH in plasma was determined in rats anaesthetized with sodium pentobarbitone. Blood samples were collected from the external jugular vein immediately before and at frequent intervals after the injections of LH-RF, and plasma concentrations of LH and, in some samples, follicle-stimulating hormone (FSH) were measured by radioimmunoassay. In rats anaesthetized with sodium pentobarbitone at 13.30 h of pro-oestrus and injected i.v. with two successive doses of LH-RF, separated by an interval of 30, 60, 120 or 240 min, the LH response to the second injection was significantly greater than that to the first. The LH response was greatest when the two doses were separated by an interval of 60 min. The FSH response to the second injection of LH-RF given 60 min after the first was not significantly different from that to the first injection. Compared with pro-oestrus, the priming effect of LH-RF was much less at metoestrus and dioestrus, and could not be demonstrated at oestrus. Ovariectomy on the morning of dioestrus reduced the LH responses to the first and second injections of LH-RF given 60 min apart on the afternoon of pro-oestrus, an effect which was partially reversed by administration of oestradiol benzoate shortly after ovariectomy. These findings together with the fact that administration of oestradiol benzoate at metoestrus increased the magnitude of the priming effect of LH-RF at dioestrus suggest that the response at pro-oestrus is dependent upon the rise in plasma oestradiol-17β which reaches a peak on the morning of pro-oestrus. Although oestrogen plays an important role in determining the magnitude of the priming effect of LH-RF, it appears that none of the steroids secreted by either the ovaries or the adrenal glands mediates this effect since the profile and magnitude of the LH responses to the two doses of LH-RF injected at pro-oestrus into rats adrenalectomized and ovariectomized before the first injection of LH-RF were comparable to those in control animals. The possible role which the priming effect of LH-RF may play in the development of the preovulatory surge of LH in the rat and man is discussed.

Effects of photoperiod on lactotrophs and on dopaminergic and 5-hydroxytryptaminergic neurones in bull calves

1991 ◽  
Vol 129 (1) ◽  
pp. 141-148 ◽  
Author(s):  
S. A. Zinn ◽  
L. T. Chapin ◽  
K. J. Lookingland ◽  
K. E. Moore ◽  
H. A. Tucker
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Plaque Assay ◽  
Brain Regions ◽  
Anterior Pituitary Gland ◽  
Pituitary Stalk ◽  
Serum Concentrations ◽  
Secretory Rate ◽  
Gland Weight ◽  
Bull Calves

ABSTRACT This study was conducted to determine whether photoperiod-induced changes in serum concentrations of prolactin in cattle were associated with changes in activity of dopamine or 5-hydroxytryptamine (5-HT) neurones in the infundibulum/pituitary stalk and the secretion rate and number of lactotrophs in the anterior pituitary gland. Sixteen prepubertal bull calves (approximately 8 weeks of age) were divided into two groups. One group of eight was maintained on a photoperiod of 8 h light : 16 h darkness (8L : 16D) and the other group was exposed to 16L : 8D for 4 weeks. At this time calves were injected with a decarboxylase inhibitor (m-hydroxybenzylhydrazine dihydrochloride, NSD 1015) which blocks the conversion of dihydroxyphenylalanine (DOPA) to dopamine and of 5-hydroxytryptophan (5-HTP) to 5-HT. Calves were killed with pentobarbital 15 min later. Accumulations of DOPA and 5-HTP in selected brain regions were used as indices of activity of dopamine and 5-HT neurones respectively. Secretory rate and number of prolactinsecreting lactotrophs were determined by reverse haemolytic plaque assay. Relative to calves exposed to 8L : 16D, exposure to 16L : 8D increased serum concentrations of prolactin by eightfold, anterior pituitary gland weight by 23%, release of prolactin from pituitary explants by 57% and the area of the plaque for prolactin-secreting lactotrophs by 70%. There was no difference in the rates of accumulation of DOPA and 5-HTP in the infundibulum/pituitary stalk of animals exposed to 4 weeks of 16L : 8D or 8L : 16D. It was concluded that increased serum concentrations of prolactin in bulls exposed to a photoperiod of 16L : 8D for 4 weeks were associated with increased secretion of prolactin from lactotrophs which was not the result of a coincident reduction in activity of dopamine neurones or an activation of 5-HT neurones that terminate in the infundibulum/pituitary stalk. Journal of Endocrinology (1991) 129, 141–148

Discovery of the luteinizing hormone of the anterior pituitary gland

2004 ◽  
Vol 287 (5) ◽  
pp. E818-E819 ◽  
Author(s):  
H. Maurice Goodman
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Anterior Lobe ◽  
Anterior Pituitary Gland ◽  
Luteinizing Hormones ◽  
Historical Significance ◽  
Classic Paper

This essay looks at the historical significance of an APS classic paper that is freely available online: Fevold HL, Hisaw FL, Leonard SL. The gonad stimulating and the luteinizing hormones of the anterior lobe of the hypophesis. Am J Physiol 97: 291—301, 1931 ( http://ajplegacy.physiology.org/cgi/reprint/97/2/291 ).

Cellular proliferation in the anterior pituitary gland of normal adult rats: Influences of sex, estrous cycle, and circadian change

1993 ◽  
Vol 235 (1) ◽  
pp. 111-120 ◽  
Author(s):  
Yuji Oishi ◽  
Minoru Okuda ◽  
Hideki Takahashi ◽  
Toshiyuki Fujii ◽  
Sotokichi Morii
Keyword(s):  
Pituitary Gland ◽  
Estrous Cycle ◽  
Anterior Pituitary ◽  
Cellular Proliferation ◽  
Anterior Pituitary Gland ◽  
Normal Adult ◽  
Adult Rats ◽  
Circadian Change

SITE OF MODULATORY ACTION OF OESTROGEN AND PROGESTERONE ON GONADOTROPHIN RESPONSE TO LUTEINIZING HORMONE RELEASING FACTOR

1977 ◽  
Vol 73 (1) ◽  
pp. 165-170 ◽  
Author(s):  
G. FINK ◽  
S. R. HENDERSON
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Female Rats ◽  
Pituitary Stalk ◽  
Spontaneous Release ◽  
Medial Basal Hypothalamus ◽  
Hypothalamic Deafferentation ◽  
Full Effect ◽  
The Brain

SUMMARY The effect of oestrogen and progesterone on the spontaneous release of gonadotrophins and on the gonadotrophin response to luteinizing hormone releasing factor has been examined in female rats subjected to hypothalamic deafferentation or pituitary stalk section. The results indicate that both steroids act at the level of the medial basal hypothalamus as well as the anterior pituitary gland; progesterone, for its full effect, also requires the integrity of connexions of the hypothalamus with other areas of the brain.

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