EFFECT OF INTRAVENOUS INFUSION OF A STEROID ANAESTHETIC ON THE PREOVULATORY SURGE OF LUTEINIZING HORMONE AND OVULATION IN INTACT RATS

1978 ◽  
Vol 76 (2) ◽  
pp. 361-362 ◽  
Author(s):  
J. RABII ◽  
D. K. CLIFTON ◽  
C. H. SAWYER
Keyword(s):  
Los Angeles ◽  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Critical Period ◽  
Brain Research ◽  
Anterior Pituitary Gland ◽  
Female Rats ◽  
School Of Medicine ◽  
Intact Rats

Department of Anatomy and Brain Research Institute, UCLA School of Medicine, Los Angeles, California 90024, U.S.A. (Received 21 July 1977) The existence of a 'critical period' in the ovulatory surge of pituitary gonadotrophin during the afternoon of pro-oestrus was demonstrated by Everett, Sawyer & Markee (1949). It was assumed that during this period, between 14.00 and 16.00 h, an amount of gonadotrophin sufficient to cause ovulation was released from the anterior pituitary gland. Administration of a number of neuropharmacologically active drugs before or during the 'critical period' was shown to inhibit the ovulatory response (Everett, 1961). Recently, Blake (1974) described the existence of an 'activation period' as well as a 'potential activation period' for the preovulatory release of luteinizing hormone (LH) in female rats. The 'activation period' is an extended 'critical period', from 14.00 to 17.00 h, during which time a neurohumoral signal continues to stimulate the anterior pituitary gland

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.

CHANGES IN THE SENSITIVITY OF THE PITUITARY GLAND TO LUTEINIZING HORMONE RELEASING FACTOR DURING THE OESTROUS CYCLE OF THE RAT

1974 ◽  
Vol 60 (1) ◽  
pp. 47-64 ◽  
Author(s):  
M. S. AIYER ◽  
G. FINK ◽  
FENELLA GREIG
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Critical Period ◽  
Standard Dose ◽  
Fold Increase ◽  
Anterior Pituitary Gland ◽  
Oestrous Cycle ◽  
Early Afternoon ◽  
Conscious Animals

SUMMARY The responsiveness of the anterior pituitary gland to synthetic luteinizing hormone releasing factor (LH-RF) was tested at various times of the oestrous cycle of the rat in order to assess the relative importance of changes in pituitary sensitivity in the timing and magnitude of the preovulatory surge of luteinizing and follicle-stimulating hormones (LH and FSH). The minimal dosage of LH-RF which consistently induced ovulation in rats anaesthetized with sodium pentobarbitone (Nembutal) immediately before the critical period of pro-oestrus was 50 ng/100 g body weight, and this was used as the standard dose throughout the study. The LH-RF was injected either intravenously into animals anaesthetized with Nembutal 30 min to 1 h before, or into conscious animals through a cardiac catheter which had been inserted several days before. Most experiments were carried out on rats which had exhibited regular 4-day oestrous cycles, although results from animals with 5-day cycles are also presented and discussed. Blood samples were taken immediately before and at frequent intervals after the injection of LH-RF, and the concentrations of LH and FSH in these samples were determined by radioimmunoassay. With respect to the secretion of LH, in both anaesthetized and conscious animals with regular 4-day cycles a tenfold increase in pituitary sensitivity occurred between the early afternoon of dioestrus and pro-oestrus. This was followed by a marked (50-fold) increase which reached a peak at 17.00–18.00 h of pro-oestrus. The phase of marked increase in sensitivity appeared to commence at about the time of the onset of the pre-ovulatory surge of LH and continued for some hours after. Pituitary sensitivity then declined through oestrus and metoestrus, reaching a nadir at 14.00 h of dioestrus. From 15.00 to 22.30 h of pro-oestrus there was a significant positive correlation between the pre-injection levels of and maximal increments in plasma LH, and this, together with the fact that the marked increase in sensitivity could be abolished by administering Nembutal before the critical period, raised the possibility that endogenous LH-RF, presumably secreted in greater amounts during the early afternoon of pro-oestrus, may exert a priming effect on the anterior pituitary gland. Pituitary responsiveness to LH-RF with respect to the secretion of FSH was also at its highest at 17.00–18.00 h of pro-oestrus. However, in contrast to LH, the mean level of FSH before injection reached a peak at 05.00 h of oestrus, 11 h after the maximum FSH response to LH-RF. These results suggest that a change in pituitary sensitivity to LH-RF may play an important role in determining the magnitude of the pre-ovulatory surge of LH, but it would appear that the timing and duration of the surge depend on other factors as well. The relationship between the secretion of LH and ovulation is discussed with respect to the finding that there appeared to be no correlation between the number of ova shed and the maximal levels of plasma LH after injection.

Further studies on the regulation, localization and function of the TRH-like peptide pyroglutamyl-glutamyl-prolineamide in the rat anterior pituitary gland

1995 ◽  
Vol 146 (2) ◽  
pp. 293-300 ◽  
Author(s):  
J M M Rondeel ◽  
W Klootwijk ◽  
E Linkels ◽  
P H M Jeucken, W ◽  
L J Hofland ◽  
...  
Keyword(s):  
Body Weight ◽  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Female Rats ◽  
Pituitary Cells ◽  
Anterior Pituitary Cells ◽  
Lhrh Antagonist

Abstract Recent evidence shows that thyrotrophin-releasing hormone (TRH) immunoreactivity in the rat anterior pituitary gland is accounted for by the TRH-like tripeptide prolineamide-glutamyl-prolineamide (pGlu-Glu-ProNH2, <EEP-NH2). The present study was undertaken to investigate further the regulation, localization and possible intrapituitary function of <EEP-NH2. Anterior pituitary levels of <EEP-NH2 were determined between days 5 and 35 of life, during the oestrous cycle and after treatment with the luteinizing hormone-releasing hormone (LHRH) antagonist Org 30276. Treatment of adult males with the LHRH antagonist either for 1 day (500 μg/100 g body weight) or for 5 days (50 μg/100 g body weight) reduced anterior pituitary <EEP-NH2 levels by 25–30% (P<0·05 versus saline-treated controls). Anterior pituitary <EEP-NH2 increased between days 5 and 35 of life. In females, these levels were 2- to 3-fold higher (P<0·05) than in males between days 15 and 25 after birth; these changes corresponded with the higher plasma follicle-stimulating hormone (FSH) levels in the female rats. After day 25, <EEP-NH2 levels in female rats decreased in parallel with a decrease in plasma FSH. Injections with the LHRH antagonist (500 μg/100 g body weight), starting on day 22 of life, led to reduced contents of <EEP-NH2 in the anterior pituitary gland of female rats on days 26 and 30 (55 and 35% decrease respectively). Levels of <EEP-NH2 in the anterior pituitary gland did not change significantly during the oestrous cycle. Fractionation of anterior pituitary cells by unit gravity sedimentation was found to be compatible with the localization of <EEP-NH2 in gonadotrophs. In vitro, <EEP-NH2 dose-dependently inhibited TRH-stimulated growth hormone (GH) release from anterior pituitary cells obtained from neonatal rats, but no consistent effects were seen on the in vitro release of luteinizing hormone (LH), FSH, prolactin (PRL) or thyroid-stimulating hormone (TSH) under basal or TRH/LHRH-stimulated conditions. Furthermore, <EEP-NH2 did not affect the in vitro hormone release by anterior pituitary cells obtained from adult rats. In vivo, <EEP-NH2 (0·3–1·0 μg intravenously) did not affect plasma PRL, TSH, LH, FSH and GH in adult male rats. We conclude that <EEP-NH2 in the anterior pituitary gland is regulated by LHRH, is probably localized in gonadotrophs and may play a (paracrine) role in neonatal GH release. Journal of Endocrinology (1995) 146, 293–300

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 ).

EFFECT OF SYNTHETIC LUTEINIZING HORMONE RELEASING HORMONE ON OVULATION DURING THE OESTROUS CYCLE IN THE RAT

1974 ◽  
Vol 76 (3) ◽  
pp. 431-437 ◽  
Author(s):  
H. Morishita ◽  
H. Mitani ◽  
Y. Masuda ◽  
K. Higuchi ◽  
M. Tomioka ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Critical Period ◽  
Early Period ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Average Volume ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh

ABSTRACT The effect of synthetic luteinizing hormone releasing hormone (LH-RH) on ovulation has been studied during the oestrous cycle in adult female rats. Ovulation could be induced by the administration of 1 μg synthetic LH-RH at 1:00 a. m. on the day of dioestrus II (lights on from 10:00 p.m. to 10:00 a.m.). At 1:00 a.m. on the day of dioestrus II, the average volume of the largest follicles reached a volume of 83 × 106 μm3 and was three fifth of the volume of that at 6:00 a. m. on the day of pro-oestrus (critical period). These findings suggest that the luteinizing hormone (LH) content in the pituitary gland during the early period of dioestrus II is sufficient to induce ovulation and that the follicles that reach to three fifth of the volume at the critical period are capable of ovulating providing endogenous ovulatory LH released.

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